The National Archives at Kew holds a millennium of documents amongst the most important in British history. Until 6 April 2023, an exhibition is open to the public, and free to attend, that focuses on the history of treason. Becoming a traitor is the ultimate act of betrayal committed against a monarch or a state.
This exhibition charts the development of treason in English law and showcases some incredible and rarely seen documents. Here are five of the best.
1. The Treason Act 1352
The Treason Act of 1352 came into force during the reign of Edward III. Edward’s grandfather, Edward I, had been accused of abusing treason laws to persecute his enemies in Scotland and Wales, perhaps most notably by executing William Wallace in 1305. During the reign of Edward’s father, Edward II, treason had been used as a weapon by opposing factions. In 1352, Edward III reset the board. The Treason Act was a contract between king and nobility that clearly identified what was, and by extension what was not, treasonable.
The definition was very narrow. It was treason to try to kill the king or his heir or levy war against them, to assault the women of his family, to give aid to the king’s enemies, to forge certain coins and seals, or to murder government officials in the course of their duty. The Act left room to develop the law further, but only with reference to Parliament. As well as protecting the crown, the Act took away a little of its power to act unilaterally.
2. Eleanor Cobham’s Trial, 1440
One document in the exhibition highlights a problem with the original Act, and with English law. Eleanor Cobham was the second wife of Humphrey, Duke of Gloucester. As a commoner, the match had caused a scandal. Humphrey was the uncle of King Henry VI and was his heir as long as Henry remained childless. In 1440, Henry seemed to be growing concerned about his uncle’s aims. His first move was against Humphrey’s wife Eleanor.
The issue highlighted by Eleanor’s case was that the law had not provided for a way to prosecute a noble woman for treason, only a man. To get around this, the documents reveal that Eleanor was put on trial in Church courts for witchcraft. She pleaded guilty to some of the charges around trying to secure fertility potions but denied she meant the king any harm.
In the secular courts, Eleanor was accused as an associate of two men who used necromancy to predict the king’s death. This loophole meant Eleanor escaped the death penalty. She was forced to divorce Humphrey and imprisoned for life. The law was changed to ensure that in future, women could be tried for treason by a jury of their peers, albeit their male peers.
3. The Act of Supremacy 1534
As Henry VIII struggled to obtain the annulment of his marriage to Catherine of Aragon, he famously broke with the Church in Rome. The Act of Supremacy wrote the creation of the Church of England into law and made it treason to call the king a heretic. Amongst the results of this momentous step would be the trial of Sir Thomas More, the record of which is also on display.
Sir Thomas was one of Henry’s closest friends and advisors. He refused to swear the oath that recognised Henry as supreme head of the church. Now, committing treason was not just an action, but could be an omission as Henry declared refusing to agree to the Act of Supremacy was treasonous.
Ironically, the woman Henry undertook all of this upheaval to marry, Anne Boleyn, would also fall foul of Henry’s wrath. Anne’s trial records describe her adultery with, amongst others, her own brother. Anne’s failure to give Henry a son doomed her, and the changes to the law brought about by Eleanor Cobham’s trial were finally put into action.
4. The Monteagle Letter, 1605
Perhaps the most famous treason trial covered by the exhibition is the Gunpowder Plot of 1605. A group of Catholic conspirators planned to blow up the Protestant King James I (and VI of Scotland) and his nobles. They planted 36 barrels of gunpowder in the undercroft beneath the Houses of Parliament, which was due to open on 5 November 1605. One letter thwarted the whole plan.
The Monteagle Letter is named after the man it was sent to. Lord Monteagle, a prominent Catholic, received a note that advised him to go to the country rather than attend the opening of Parliament. The letter asked Lord Monteagle to burn it once he had read it, but instead, he handed it over to the authorities, sparking the search of Parliament that found Guy Fawkes and the gunpowder.
There remains doubt about who wrote the letter. Was it Monteagle himself, seeking to expose a plot he disapproved of? Was it from one of the conspirators, but Monteagle feared it was a test of his loyalty by the authorities. Wherever it really came from, it’s the reason the Gunpowder Plot failed.
5. The Trial Diary of Charles I, 1649
One set of documents within the exhibition demonstrates a dramatic change in treason law. In January 1649, King Charles I was put on trial for treason. Parliament had to create a whole new court, because treason was usually tried in King’s Bench, where justice flowed from the king. Charles refused to recognise the authority of the new court, or to enter a plea.
The diary of his trial details how Parliament contrived to find Charles guilty of treason against the state, a kingdom he claimed to rule by God’s divine authority alone. On 30 January 1649, Charles was executed for treason against the state of England. An Act designed to protect the monarch had been turned against one. It had always been about taking away power too. In 1649, the shield became the sword.
The Treason Act 1352 is still part of UK law today. The last person executed for treason was William Joyce, also known as Lord Haw Haw, a Nazi radio propagandist during World War Two. He was hanged on 3 January 1946. You can no longer be executed for treason, though it does carry a life sentence. The story of treason law is a fascinating journey that helps to chart the emergence of a nation state in England. You can visit these key documents and more for free while the exhibition runs at the National Archives.