♪ ♪ -Mary, Queen of Scots... one of the most famous and controversial monarchs in British history.

During a tumultuous life, much of which she spent imprisoned, Mary was a prolific letter writer, smuggling out hundreds of letters -- all written in secret code.

[ Dramatic music plays ] While a number of these documents have been discovered and decoded, a collection dating from 1578 to 1584 were believed to be lost or destroyed... until a trio of amateur codebreakers started working together to decipher this obscure cache of coded messages and reveal a new picture of the tragic queen's life.

-Knowledge is power, information is power.

And the best way to get that is really through letters.

-Oh, it's beautiful.

-Wow!

-When we look at her letters, we do get a real sense of this is a woman who is directing the events around her.

-Containing mentions of spies, poisoning, and a treacherous son, these letters reveal the tenacity of Scotland's most famous queen -- and that of the enemies determined to bring her down.

-Mary's terrible crimes are that she's powerful, she's very beautiful, and she's very young.

-Mary is someone who survives, I think, against the odds.

She's someone who doesn't give up.

-The story has a huge amount of drama.

It has murder, it has sex, and it has a very dramatic and tragic end.

-Incredible!

♪ ♪♪ -Mary Stuart has been Queen of Scotland since she was just six days old.

As a child, she lives in France while her mother, Marie de Guise, rules Scotland as regent.

-Some of her kind of earliest surviving letters are letters that Mary writes to her mother when she's only between 8 and 10 years old.

-Mary is promised in marriage to Francis, the heir to the French throne.

Related to both Henry VII and Henry VIII, she is also in the line of succession for the English throne.

From an early age, Mary must learn how Europe's powerful dynasties communicate in secret.

-Mary is being taught how do you send secret messages.

We see in her letters to her mother, her getting quite excited about this new skill.

-"I would have written to you in cipher, but my secretary told me that there was no need and that he would write to you in cipher himself."

-Your entry-level code would just be giving alternative symbols for people's names.

Then there are more complicated codes where each letter of the alphabet has a substitute symbol, and more complicated still are ones where you would have false signals put in there as well.

-It makes it much harder for anyone to read it should it fall into, you know, unwanted hands.

-It's really essential to doing any kind of sensitive politics in this period.

-The coding systems that Mary used in her letters changed constantly, evolving in complexity, making them almost impossible to decipher... ♪ ♪ But patent expert Satoshi Tomokiyo has been an amateur codebreaker since he was a child.

[ P.A.

announcements in Japanese ] -Decrypting secret codes is a fascinating thing.

It's like solving a puzzle where, little by little, an incomprehensible text makes sense.

♪ -Satoshi trawls the digital archives of European institutions for unpublished, encrypted documents written by 16th-Century monarchs, generals, and popes.

[ Keyboard clacking ] ♪ In March 2021, searching through the National Library of France, he came across a mysterious batch of 26 letters, filed as relating to Italy.

-Encoded documents didn't contain any information about who wrote them or when they were written.

Everything was in code.

♪ -Satoshi posts a link on his website inviting other codebreakers to answer the questions surrounding the letters: Who wrote them?

What do they say?

[ Waves crashing ] [ Kids shouting ] On the other side of the world, computer scientist George Lasry spots Satoshi's post.

-I started to be interested in secret codes by chance, about 10 years ago?

I was unemployed and needed to find work.

To keep busy, I decided to get back into programming.

I started trying to crack codes.

Little by little, it became something of an obsession.

[ Dramatic music plays ] -Meticulous and competitive, George has become one of the world's top codebreakers.

-In principle, breaking a secret code is an intellectual and interesting challenge.

But it's even more interesting when it's a true code -- a historical code that was actually used by someone.

-George tries new software he's developed that uses computing algorithms to help analyze sophisticated codes.

-It's a software that is really dedicated to the decryption of historical codes and allows not only numerical entry, but also cryptanalysis.

At the time, were no tools like that -- I had to develop it myself.

-He makes his first attempt at decrypting the letters Satoshi has found, believing they're written in Italian.

-I do several tests, I change some parameters of the software, but that makes no difference.

I search really thoroughly for words in Italian, but I can't make any sense of it.

[ Suspenseful music plays ] ♪ -Neither George nor his software can make sense of the text, and he moves on to other projects... ♪ [ Dramatic music plays ] Mary flourishes, growing up at the French court, destined to be queen of both Scotland and France -- and perhaps more.

-She's a big hit, basically.

She's a really pretty child, she's a very quick-witted child.

She likes to dance, she likes to laugh, she likes to play, she's quite gifted musically, she's good at foreign languages.

[ Choir chanting ] -The King, Henry II, just really is obviously enchanted by her.

-He wants to see his family take over the world.

And he sees in Mary someone who has the throne to Scotland, and also a very strong claim to the English throne -- a way to expand that reach into the British Isles.

-Mary is now a key player in the dynastic rivalry between England, France, and Scotland -- a rivalry deepened by religious differences.

A revolution in faith, the Reformation that started in Germany swept north across Europe.

[ Classical music plays ] -Reaching England and really getting roots in the English court in the 1530s is the idea that you should break away from the Catholic Church, embrace a new form of Christianity: Protestantism.

-Scotland, like its ally France, holds out as bastion of Catholicism.

In 1558, when Mary weds the dauphin Francis at Notre Dame in Paris, the lavish religious ceremony sends a message: Scotland and France are Catholic.

-It's one that's done with public relations in mind.

This is the strength of the new Franco-Scottish monarchy.

And she tells her mother, "I'm one of the happiest women alive."

[ Dramatic music plays ] -When Mary I of England dies that same year, 15-year-old Mary Stuart becomes a contender for the English throne, as she too has Tudor heritage.

Catholics promote her claim -- but it's her Protestant cousin who takes the throne as Elizabeth I.

-Elizabeth is the daughter of Henry VIII's second marriage to Anne Boleyn, so in Catholic eyes she's illegitimate because they don't recognize divorce.

-So that gives Mary powerful international leverage.

She is descended from the Tudor line, and she is also a devout Catholic.

-As Elizabeth I begins her reign in England, she is immediately threatened by this pushy expansionist claim from France, from Scotland.

Mary's full of it, her in-laws are full of her, her own family are full of it.

If you're Elizabeth and you're the Protestant regime around her, you're feeling extremely threatened.

-The French happily add more fuel to the fire.

-It's her father-in-law, Henry II, who really encourages her to incorporate the English coat of arms into her coat of arms.

It's red rag to bull to Elizabeth.

♪ -The English queen uses the thorny issue of religion to retaliate.

Because Elizabeth sees her royal authority threatened by Mary's claim to be Queen of England, she decides, all right, well, I will help the Scottish Protestants.

-By 1560, there is a Reformation rebellion led by a group of nobility and they, in effect, create a Protestant settlement almost overnight at the Parliament in August 1560.

-No more Pope.

No more mass.

Scotland has broken from Rome.

[ Dramatic music plays ] ♪ -Nine months have passed since George I looked at the encrypted letters found by Satoshi -- and he decides to have another go at the code.

-A starting point is that this is a homophonic code, where there are several symbols to represent each letter of the alphabet.

-Almost all the codes of that time are homophonic codes.

And the second characteristic of the codes at the time is the repertoire or the nomenclature.

It's a list of symbols that are assigned to elements of the language that are not individual letters of the alphabet -- for example, prepositions or words, or parts of words, suffixes or prefixes.

And also proper names: names of people, cities, countries.

[ Suspenseful music plays ] ♪ -George starts to wonder whether the letters really are in Italian after all... ♪ [ Dramatic music plays ] ♪ Over the next 18 months, Mary's life in France changes dramatically.

-She goes through a really traumatic time.

She loses three of the most important people in her life.

-Mary's father-in-law, Henry II, is killed in a jousting accident.

Her mother dies in Edinburgh.

There are rumors of poison.

And then her husband, the new King Francis II, dies of sepsis.

Mary's power in France is slipping away.

She sends out letters to supporters hoping to shore up her position.

-Mary tries to find another alliance in Europe, but realizes that that's not a possibility and she starts to look at returning back to Scotland.

[ Down-tempo music plays ] ♪ I think returning to Scotland would have been really hard for her.

She probably has very few memories of Scotland.

But she's also very consciously aware that Scotland has recently gone through the Reformation -- it is now a Protestant country.

♪ -When she first arrives in Edinburgh, it must have seemed fairly backwards because it's full of, frankly, very small angry men -- unlike now.

[ Laughs ] ♪ -She is a Catholic in a country that has just enacted a very militant form of Protestantism.

-She and her subjects are eyeing each other up.

Which way is she going to jump?

The Catholic Queen returning with a letter from the Pope encouraging her to return her country to the Catholic faith.

-Mary remains a devout Catholic, but she opts for a pragmatic way forward on religion.

-Her religious policy in Scotland is canny, shrewd, sensible.

-One of the first proclamations that she releases says there will be no change to the religion as she finds it established in Scotland -- but she will claim for the right to a private mass for herself and her household.

-Mary's uneasy compromise with the Scottish Protestants holds for now... but it will prove to be a constant source of danger for her.

[ Kids shouting ] [ Soft music plays ] ♪ George acts on a hunch: What if the letters were misfiled and are actually written in French?

-I said, "Well, it's at the BNF, why not try French?"

And then I press the button.

In a few seconds, I see words in French.

I say, "Oh, that's great, it's in French!"

It's very good.

I'm very happy.

-At last, what seems like a breakthrough: Syllables and fragments of French words start to appear in the lines of code.

-I'm moving forward, I'm trying to complete.

In general, when I get to this stage, it happens very quickly.

But in this case, I'm stuck.

It doesn't happen to me very often.

I say to myself, "What am I going to do now?"

-But despite now knowing the language, many symbols remain meaningless.

-Before I ask for help, I have to put my pride aside first, because I usually work alone, and I like to break these codes by myself.

But I recognize, first, the code seems to be quite complicated because there are about 200 distinct types of symbols.

And second, there's a large number of documents.

And I think maybe this is a time to ask for help.

-George sends a message to codebreakers he usually sees as rivals: Satoshi, who found and shared the cache of letters, and another cryptographer, Norbert Biermann.

[ Up-tempo piano music plays ] ♪ -Norbert lives and works in Berlin.

As both a professional pianist and a professor at the Faculty of Arts, he spends his days immersed in another form of code: sheet music.

-[ In German ] When you do my job, you have to know how to read and play a lot of notes.

You have to decipher them on first reading.

♪ So, at first sight, music and cryptology may not appear to have much in common.

But there are still these small points of contact -- and one of them is language.

I received a message from George Lasry: [ In English ] "Help needed with French cipher."

[ In German ] My help!

[ Chuckles ] And of course, I felt very honored.

[ Dramatic music plays ] ♪ -Norbert, George, and Satoshi agree to join forces to try and crack the centuries-old cipher and find out who wrote the letters... ♪ However popular Mary is for now, she must still deal with an issue unique to female monarchs of the time.

-For a queen, if they marry, then their property becomes the heritable property of their husband, which immediately poses a huge issue for someone like Mary, because that is, in effect, her crown matrimonial -- the right of her family would pass to her husband.

And Elizabeth chooses not to marry, famously -- effectively becomes married to the realm of England.

And these are all different tactics that can be used.

So, it's a real issue for a queen.

If you marry, what does that mean for your own sovereign power?

-But a very tempting marriage opportunity arises for Mary: her cousin, Henry Stuart, Lord Darnley.

-Darnley looks good on paper because he is from a Scottish family, but has a line in the English succession.

-Together, Mary and Darnley have a very,very powerful dynastic claim to the English throne.

I think Mary is looking at him very clearly as, "You're what I need to get the English succession secured."

-He's young.

She thinks he might be manageable.

He is religiously ambiguous.

-And when she meets him as well, there is, of course, an element that's noted by a number of contemporaries of physical attraction.

-And she says he is "the best long man I have ever seen in my life."

Everyone fancied Darnley.

And she marries him, and I think they don't get out of bed for the first four days of their marriage.

-Yet, Mary's decision to marry Darnley is also a big risk.

-The marriage to Darnley is pursued without parliamentary approval in Scotland, and it's pursued without Elizabeth's approval, as well.

And that in itself leads to an alienation of the main council that had been in support of Mary through the first half of her reign in Scotland.

[ Thunder rumbling ] -Protestant lords mount a rebellion against the marriage... but the uprising is short-lived.

And initially, Mary's choice proves to be a smart one... in a crucial way.

[ Dramatic music plays ] ♪ -Mary gets pregnant.

It's a healthy pregnancy.

-She achieves what England's queens, Mary Tudor and Elizabeth I, never do.

But her husband is not what he seemed... -Darnley is developing a nasty temper.

-He's also lazy, he's dissolute, he disturbs politics.

-He couldn't keep his trousers on.

He has parties in whorehouses in Edinburgh.

He gets far, far too drunk publicly and begins to shame her.

-He's also very clear that he should be named King in his own right.

And he's expecting that from Mary.

And when he doesn't get it, he becomes very, very difficult.

-He starts to go hunting when she needs him to co-sign legislation.

He's trying to blackmail her into giving him the power that he wants.

-They create a rubber stamp that has his signature on it for managing documents.

-She gives it to her secretary, David Rizzio, and Rizzio starts replacing Darnley in the state function.

-Jealous of Rizzio, Darnley conspires with Protestant lords concerned that Mary is favoring Catholics politically.

-They seize Holyrood Palace and force their way into Mary's chambers.

-Mary's six months pregnant.

She is having a dinner party.

They come into the dining room, and they say to Mary, give us David Rizzio.

They drag him out into her audience chamber, and they all stab him.

56 stab wounds.

This is Julius Caesar like 20 years before Shakespeare wrote the play.

-Darnley's dagger is left in the body so that Mary is very clear that this is something that her husband has supported.

-Mary's survival instinct kicks in.

-She's able to convince Darnley that the plotters are really against him as well as against her.

-And Mary says, "Look, they're gonna kill you."

So, he says, "Please protect me, please help me to make it right."

-And she does.

And she has the composure to do that and to secure their escape and flee from Holyrood.

Bearing in mind she is heavily pregnant, she's been assaulted by these men, she's seen the brutal murder of one of her close personal favorites -- to get up and walk away from that and salvage success does take real steel.

-With the help of an ally, the Earl of Bothwell, Mary gathers forces and regains control.

And then, in June 1566, she achieves the ultimate goal: she gives birth to a baby boy.

-Is this not a sign of divine favor?

Is God not smiling on the Queen of Scots and her kingdom that she has a healthy male heir?

This is the dynastic trump card.

-James physically combines both Darnley and Mary's claims within him.

-And when we see the accounts of Elizabeth hearing that Mary has given birth -- not just to a child, but to a healthy baby boy -- we see how much political strength Mary has.

The account from the Scottish ambassador is that Elizabeth immediately sat down, all merriment was put aside for the evening, he says, and the Queen rests her head on her hand, and she says, "The Queen of Scots is lighter of a fair son, and I am but a barren stock."

[ Suspenseful music plays ] ♪ -But securing a male heir to the Scottish throne is not enough to protect Mary.

Her husband's abusive behavior only gets worse.

-Darnley doesn't turn up to his own son's christening.

He actually says this baby might be David Rizzio's baby.

David Rizzio was Italian.

James VI is as ginger as a baby comes.

I mean, he's very clearly a Scottish baby.

-Mary is clear she cannot have a divorce, because if she does, that would effectively make her son illegitimate.

So, she's really looking for an annulment or some other reason why the marriage could be invalidated, but James's legitimacy would not be.

-Another, more violent solution presents itself.

-Darnley's end was quite unpleasant, even for a horrible person, he probably didn't deserve what happened to him.

-Darnley has fallen unwell, and Mary takes him to Kirk o' Field just outside Edinburgh to nurse him, to look after him.

-Someone has got masses of barrels of gunpowder and packed them into the room below his bedroom.

They blow him up.

[ Dramatic music plays ] -He's found outside the smoldering remains of the house.

He's half-dressed, strangled to death, with one of his servants.

Everyone knows it's a murder.

It's not natural causes, put it that way.

-So, immediately, there are elements that say: How far was Mary involved in this?

♪ [ Suspenseful music plays ] -The trio of codebreakers are immersed in a mystery of their own: Reconstructing the key to the code -- the secret information that unlocks the cipher... and dozens of cryptic characters that signify names and locations, as well as common words.

-The software only gives us the meaning of the letters of the alphabet.

It allows you to decipher part of the text -- but to decipher the rest of the text, you have to interpret other symbols that aren't necessarily letters of the alphabet.

-But it turns out it's even more complex.

We are far from being able to solve everything.

And there are still a lot of texts to be transcribed.

-Despite the complexity, the team is starting to decipher some of the unique symbols.

-There are very specific symbols.

The one I call the symbol that erases -- the Tipp-Ex symbol, if you like -- it simply cancels the symbol that precedes it.

That's to say, we see any sign followed by this "eraser" symbol -- it looks like an oblique exclamation point -- and it erases the previous one.

It can be used to cause confusion, or simply when they have made a coding error.

Then, there is a symbol that duplicates the symbol that came before it.

♪ And then there's the "null" symbol.

It doesn't mean anything, but it's often used as a period or comma, to separate ideas or sentences.

The big challenge especially is that there's no punctuation in these letters.

That is to say, according to logic, we must understand the context -- where to put the period, where to put the commas.

And sometimes, a misplaced period or comma can completely change the meaning of a sentence.

-Beyond the punctuation and obscure Renaissance-era French, essential questions remain unanswered for the codebreakers -- They still don't know who wrote the letters or why.

Mary faces her own troubles.

Rumors swirl that her ally, the Earl of Bothwell, is complicit in Darnley's murder.

They grow so strong, he is put on trial.

But Edinburgh is packed with his supporters, and he is acquitted.

-It's a really messy time for Mary because Bothwell is her source of support at this moment in time, and yet he is the person regarded as having murdered her husband.

Bothwell's fingerprints are all over it.

-After Darnley's assassination, Bothwell moves very quickly to control the Queen.

Bothwell wants to be king, and he thinks with Darnley out of the way, he sees a chance.

-Mary is taken to Dunbar Castle with Bothwell, and there it seems very likely that she is raped.

As awful as it is, he's thinking that "If I rape Mary, then essentially that gives me complete control over her" because even the hint of adulterous marriage, sex outside marriage, or if she becomes pregnant -- both those things would completely destroy her standing as a queen and it really leaves her with no option but to marry him.

-So, she's trying to correct the rape by marrying Bothwell.

And it goes disastrously wrong because he is not popular, he is not trusted.

-Increasingly resentful of Bothwell's new status, many Scottish lords rebel.

-It's an overwhelming force arrayed against Mary and Bothwell, and Mary gives herself up and Bothwell flees.

She is initially paraded into Edinburgh and there are cries of "kill the whore."

-She has lost the love of the people because the story line is just too complicated now.

The main lords in Scotland then take her off to Lochleven Castle where she's imprisoned.

-And it's there that she is forced to sign a series of abdication documents that cede the throne to James.

At this point, she is very likely pregnant with twins and miscarries -- so it is the lowest point of her life, by all accounts.

Her son from Darnley, now proclaimed James VI of Scotland, will be raised Protestant.

-He was a triumph when he was born, and now he becomes her weakness because now they can get her to abdicate.

They no longer need her.

She is superfluous to requirements.

-But Mary continues to fight for her authority.

A year later, in 1568, the 25-year-old queen makes a daring escape, insisting she was coerced into signing abdication papers and that she remains the rightful queen of Scotland.

She raises an army -- but is defeated again and feels forced to flee.

♪ -Along with the Darnley marriage, you could argue that this is where she makes the other greatest tactical error of her career.

She thinks, "I'll go to England."

It's a relatively short crossing across the Solway, and she thinks that Elizabeth will harbor her.

From her perspective, she and Elizabeth are both female monarchs.

They have both been faced with challenges to their authority as a result.

They are also kin.

-Mary, not unreasonably, believes that if Elizabeth hears that these people are rebels, that she will support her.

-Mary writes to Elizabeth.

-"...those of all my subjects to whom I had done the most good have driven me entirely from my kingdom and reduced me to such a state that after God I have no other hope than in you."

-But Mary has miscalculated.

She thinks, "If I go to England, I will still be a recognized queen."

And it's that, I think, that absolutely astonishes Mary when it becomes clear that she'll be recognized only as a prisoner.

-Mary will spend the rest of her life -- 19 years -- in captivity in England.

♪ The three codebreakers are now working obsessively, deciphering letters around the clock.

They know what kind of code it is, they know it's in arcane French, but they're still trying to identify the author.

Finally, vital clues emerge.

-When I see, for example, "my son," then it's someone who has a son.

Then I see the word "freedom" and "my freedom."

So I say to myself, will someone who is free necessarily talk about their freedom?

No.

In my opinion, it's someone who is not free, someone in captivity.

Then, at the end of the first letter, I see the word "occupee" with two E's at the end.

Okay, it's a feminine adjective and it was from a woman -- a woman in captivity, who has a son, who writes in French.

We're getting somewhere.

-Suddenly, amid the noise of symbols, a name surfaces -- "Walsingham."

The name of a man legendary in codebreaking.

♪ ♪ -Sir Francis Walsingham was the spymaster for the queen, Queen Elizabeth I. The Queen, particularly because of the conflict between the Protestant and the Catholic groups in England in that period, had to have a very well-developed intelligence capability.

And Sir Francis Walsingham, I think I would see as the first person who made intelligence work a proper profession.

The fundamental job of Walsingham, which was to keep the country safe from the Queen's enemies, is the same as it is today for MI5 and for the British intelligence community.

♪ -Walsingham haunts George's sleep.

What prisoner could link Elizabeth's spymaster to these coded letters?

And then it hits him.

At 2:00 a.m., he e-mails his fellow codebreakers -- "I'm beginning to suspect that these letters are from Mary Stuart."

♪ -For me it took a bit of time.

At first, I was a bit doubtful.

I am the doubtful type.

I always want to know exactly what's going on before I get carried away.

But if the letters really are from Mary Stuart... that's great.

That's really exciting.

♪ -At first, I was also skeptical, but the very next day the other proper names appeared, and I was convinced that these documents were in fact linked to Mary Stuart.

-As soon as we realized it was Mary Stuart, it was incredible.

I think we hardly slept for several nights.

It was really very exciting.

♪ -The team realizes that these are lost letters from the most dangerous period in Mary's life, when she was imprisoned in England and kept under close surveillance by Walsingham's web of informants.

Walsingham is Mary's nemesis.

She writes in one letter... -"Watch out for Walsingham because he's a clever man and master deceiver."

♪ -The religious atmosphere in England remains febrile.

Mary's presence as a Catholic queen is a huge headache for her cousin Elizabeth and her regime.

-There is a strong and vocal minority of Catholics that would like to see a removal of Elizabeth from power, or at least more toleration given to the Catholic faith.

-The fact is that Elizabeth is surrounded by Protestant advisors who think that Mary is effectively the closest thing on this earth to the devil incarnate.

They don't want Elizabeth anywhere near her.

-Elizabeth is also wary of meeting her, apparently, because she thinks Mary will get the better of her in an argument.

-Mary thinks, probably correctly, if she can see Elizabeth face to face, she will get some degree of support from her.

Elizabeth doesn't want to be boxed into that corner.

-She has to just avoid it entirely.

Just push it down the road as far as she can.

She manages to go the full almost 20 years without meeting Mary.

-George Talbot, Earl of Shrewsbury, is charged with supervising Mary while she's in captivity and moves her from castle to castle in northern England.

-Although it's captivity, she is still a queen.

She has her own household within the Shrewsbury's household.

-For Mary, who is never allowed to actually move beyond the confines of these various properties, it is quite monotonous.

It's quite repetitive.

-She finds something else to do, and that is she writes letters, endlessly.

She is writing to powers all over Europe, she writes to the papacy, to Philip II of Spain.

-We see Mary using letters as a means of positioning herself at the center of a network that crosses Europe.

-As far as she's concerned, throughout this period, she is the rightful queen of Scotland who's been forcibly removed.

And in her own mind as well, she is the lawful Catholic sovereign of England, as well.

So, for her, it's all to play for.

-Persuasion, plots, even proposals of marriage -- Both her official correspondence and secret coded letters reveal the different strategies Mary uses to try and free herself from captivity and regain her crown.

-You really see just how politically astute and politically aware she is.

She does not give up.

-Dr.

Alexander Courtney is the author of a biography of Mary Stuart's son, James VI of Scotland -- a book inspired by doctoral research he did at Selwyn College, Cambridge.

The codebreakers have asked for his help as an expert in Middle French, spoken during the Renaissance.

-I was the first historian to read them since they were enciphered, and to have them on my laptop in front of me, that was really astonishing.

It was apparent that these letters would be a very rich source.

And that they're a really complex source as well.

-As Alexander starts a detailed translation of the decoded French, Norbert has been working on a complexity in Mary's code.

He finds the meaning of some symbols is altered by subtle additions of a dot, comma, or accent.

-This is a particular characteristic of this cryptogram.

We talk about a diacritical symbol.

What does this mean?

In fact, it changes the main symbol.

For example, we have a symbol that looks like a small "O," but it represents the letter "A."

Diacritical symbols can be added to it.

If there is a dot behind this "O," then it means "-ance," the French word or suffix "-ance."

If the dot is placed under the symbol, it then means -- be careful, it's a long word -- "my brother-in-law."

Just because the dot is placed, it becomes "My brother-in-law."

It's these two diacritical symbols.

George had already spotted them.

But then, after a few days, I discovered that there are others.

You can also put a comma afterwards, and then that means "letter."

Or you can add a slash behind it and that means "king."

So, that's four different ways to change the same symbol.

So, we find that one single symbol can have up to five different meanings.

-The letter "K," Norbert determines, is usually code for the French ambassador, Michel de Castelnau de la Mauvissire.

An ally and friend of Mary's since childhood, the majority of these new letters are addressed to him.

Mary knows her letters are being intercepted.

Some she dispatches officially via what she calls "Walsingham's way," aware that the spymaster will read them before sending them on.

-There are other ways of getting letters through.

These secret letters are the ones which were likely to be encrypted by one of her two secretaries.

-She has a French secretary, Claude Nau, and she has a Scot secretary, Gilbert Curle.

Sometimes when she folds letters up into those tiny little packets, she's able to have her ladies smuggle them out by slipping them up the sleeves of their dresses.

-Sometimes they're put in the heel of a shoe.

-Or she's slipping them into the bindings of books.

Her ladies, quite often, when no one's looking, leave them at certain locations in the garden, often, you know, under stones.

There are reports by Mary's longtime custodian, George Talbot, the Earl of Shrewsbury, where he has found letters that have been hidden in the garden.

And so, as those clandestine opportunities are diminished, she realizes that she has to somehow come up with another way to try and avoid detection by Walsingham and his agents.

-So Mary starts a secret channel through the French Embassy.

She sends letters that will be protected as part of the official, diplomatic correspondence of France.

-There's the potential to just sneak a few other little things into the diplomatic bag.

And so, the French Embassy also becomes a route through which Mary's secret correspondence can be fed, first into London, and then onwards into Europe.

-For several years, the route is secure.

But it's all based on trust -- and in 1583, Mary begins to suspect there's a mole working against her at the Embassy.

-She is aware of Walsingham's methods, she's aware that he uses double agents, and she becomes increasingly concerned there's someone within the French Embassy who she can't trust.

-As more and more letters start to disappear or take longer to reach Mary, she goes back to Castelnau and she says to him, "You need to look at your people because someone is passing information.

There is a leak in the Embassy."

♪ -Sifting through the codebreakers' work, Alexander Courtney is finding fascinating details about how Mary pushes to improve the conditions she's held in.

-Mary's finances are a theme through the letters.

She is very frequently in a position where she is complaining about not having enough to pay the wages of her servants.

This is F89, dating from April 1583 here -- "Il n'est dans mon puissance de faire fond d'un seul denier au bout de l'an."

So, it isn't in her power to set aside almost a single silver penny for the end of the year.

-It's essentially a small court in exile.

It costs a fortune to run, even with her own inheritable funds from her dowry.

-Again and again in her letters, Mary complains about the impact captivity has had on her health.

-She can't go riding or hunting the way she would have liked to do, and that limited physical movement is quite hard for her.

-"What little freedom I had left has been taken away from me, and they still want to force me to stay in my room, even though for over a year I haven't left this house further than an arrow's throw."

-She suffers from neuralgia, she has headaches, she gains weight, and she has a load of physical health complaints associated with that.

-She actually uses the language of illness in her letters to Elizabeth as a means of almost shaming Elizabeth, almost saying, you know, "This is what you have led me to."

-The coded letters reveal some outlandish therapies prescribed by English doctors -- possibly with sinister intent.

-It's suggested, for example, that she ought to drink a preparation with gold in it.

And she says, you know, "No, I don't want that."

Potentially this speaks to her fear of being poisoned.

And she's worried she's going be a victim of assassination, so her own people make her food.

-Alexander discovers another recurring theme within the cipher.

-One of the most repeated phrases of the letters is "Mon fils" this, "Mon fils" that -- "my son" this, "my son" that.

She expresses occasionally a sentiment that she lives only for the future of her son.

-The coded letters refer to a new plan Mary has to gain her freedom.

She enlists the help of her son -- who now, in the 1580s, is coming of age as King of Scotland.

-Mary puts forward a scheme known as the Association, where she effectively says to James, "Look, why don't we rule together?"

-The Association proposal becomes a negotiation between Mary, James, and Elizabeth.

Mary is prepared to renounce her claim to the English throne as part of a deal for freedom.

-In here, Mary is really pushing for it.

James writes to his mother and says, "I love and honor you.

I will do whatever I can to support you in this."

But in reality, he was playing her off and trying to get leverage.

-James, by this point, he's very much his mother's boy, very much a Stuart.

Having got power, James is not inclined to share it.

-James negotiates with Elizabeth behind his mother's back.

-He recognizes that if he works with Elizabeth and negotiates with her, that he will become the de facto heir to England.

And he immediately cuts off discussion about the Association with his mother.

-This is a young man who's had no physical contact with his mother since he was a baby.

He's been raised by people who have tried to prevent him from having any positive interactions with his mother.

-He gives her over to her enemies, and that really breaks her.

She's bitter for the rest of her life because of that.

-"If my son persists, I will invoke the curse of God against him, disinherit and deprive him, as an unnatural, ungrateful, treacherous, and disobedient son."

-After the Association, you start to see Mary become much more frustrated with her position.

It's a case of her options running out.

-By the mid-1580s, ever more desperate to escape her imprisonment, Mary gambles on plots hatched by her Catholic allies.

The Throckmorton Plot, involving a raid to free her, is foiled by Walsingham and his network of spies.

Then, in 1586, a daring new plot, led by English Catholic Anthony Babington, presents Walsingham with an opportunity.

-Over time, the Babington Plot develops into something much more dangerous.

It develops into a plot that not only seeks to free Mary, but aims to assassinate Elizabeth in the process.

-The Babington Plot is one that she doesn't realize at the time is a sting.

It's essentially being engineered by Walsingham and the intelligence network around him.

-He sets up the evidence to fall a certain way.

-And she's hiding coded messages and sending these out.

But what she doesn't realize is they're being intercepted immediately.

They're being opened, they're being read, they're being closed, being sent on again.

Mary is only presented with this knowledge at her trial, and she is shell-shocked when she realizes they have all this.

That is the end.

She really does realize, "Oh, wow, there's no real way out of this for me."

-Mary's downfall is rapid.

In October 1586, she is found guilty of treason.

The execution of a monarch -- a dishonorable traitor's death -- shocks Europe.

Despite this, Mary retains control of the narrative.

-"In my end is my beginning."

She could be saying, you know, "I am going into the afterlife as a martyr."

She has kept her faith.

She has never wavered.

I think Mary is referring to, "You might execute me, but my line lives on, in James."

So even though James had gone behind her back, she still understands that he will go on to inherit what she did not.

-Brought to the block in front of English noblemen and other witnesses, Mary makes her final, triumphant move.

-One of the shaming things of the execution is going to be that she will be required to disrobe in public.

It's designed to humiliate her.

So, when her outer garments are removed, rather than standing in shame, she appears in glorious crimson red.

The color of martyrdom.

This is political theater at its absolute finest.

-She knows it's going to be reported across Europe.

So, she's thinking long-term, and saying, "I'm undiminished.

I am defiant in the face of you."

♪ ♪ -400 years later, Mary lives on in her letters.

In November 2022, the codebreakers complete their work.

They've deciphered almost 50,000 words in some 50 previously unknown letters written by Mary, Queen of Scots.

The story becomes world news.

-Now to an incredible discovery involving treason, espionage, codebreaking, and Elizabethan intrigue.

More than 50 letters written in cipher sent by Mary, Queen of Scots... -I was interviewed by dozens of media companies -- The New York Times, the BBC, The Washington Post, Le Monde, Der Spiegel -- hundreds of interviews in three or four days.

It was crazy.

♪ -Monsieur, je vous accompagne au Salon des Lettres, la salle de la consultation.

Vous allez pouvoir rencontrer Camille Desenclos... -Up to this point, the codebreakers have only been able to work with digital images of Mary's letters.

Now, George and Norbert visit the French National Library.

-Oh, it's beautiful.

-Wow!

-Yes, it is.

-They come face-to-face with the original, historic documents for the first time.

-This is the longest one, 8,000 symbols.

-Really?

-Yeah.

-Yes.

And so... -And this is handwriting of Jacques Nau, the secretary.

-Probably, yes.

-Probably.

-Yeah, they never signed... -Mm.

Probably right.

-...but it's definitely a clerk handwriting.

-Wow, that's exciting.

Okay, the post-script is from her?

-Yeah.

-All right, wow, that's fantastic.

Wow.

Incredible.

[ Line ringing ] -Hey, Satoshi!

Hi!

-Hi, George!

-We are here today with Camille Desenclos and Norbert... -Hi Satoshi!

-...and I also want to show you, of course, the document.

-Yes, I now see it.

-And Satoshi, you can't believe how small the letters are, the symbols.

It's so -- it's unbelievable.

-But it is fantastic to see them.

It's really something very, very unique.

-The new letters deciphered by the codebreakers create a clearer picture of Mary, Queen of Scots' long years of captivity... of her isolation and paranoia... as well as her justified suspicion of Walsingham and his spies.

-The fact that the team managed to find 50-odd letters that are attributed conclusively as Mary's for the first time is a remarkable achievement.

The letters themselves corroborate things that scholars and historians have suspected for a long time, but we thought the evidence had been destroyed.

-There are 50,000 or so new words of Mary, Queen of Scots here.

People will be working on these letters for many, many years to come.

-Mary and Elizabeth, the rival queens, famously never met.

But ironically, they're now close neighbors.

-Mary's son, a Stuart, succeeds Elizabeth to become King of England in 1603.

And he moves his mother's tomb to Westminster Abbey, where Elizabeth was also laid to rest.

-She lives through and reigns through a really problematic time.

She produces an heir and secures the succession of her kingdom, and James goes on to inherit the thrones of England and Ireland as well.

-For too long, I feel like Mary has been seen as someone who is either romanticized, or she's been demonized as this person who got above her station.

But her letters really give the sense of a person -- a person who, regardless of how difficult things become for her, she's convinced of her status as a queen, she's utterly convinced of who she is.

-As Mary herself said, "As an absolute Queen, I cannot submit to orders."