Under the law of the United Kingdom, high treason is the crime of disloyalty to the Crown. Offences constituting high treason include plotting the murder of the sovereign; committing adultery with the sovereign's consort, with the sovereign's eldest unmarried daughter, or with the wife of the heir to the throne; levying war against the sovereign and adhering to the sovereign's enemies, giving them aid or comfort; and attempting to undermine the line of succession to the Throne. Several other crimes have historically been categorised as high treason, including counterfeiting money and being a Catholic priest.Jesuits, etc. Act 1584
High treason was generally distinguished from petty treason, a treason committed against a subject of the sovereign, the scope of which was limited by statute to the murder of a legal superior. Petty treason comprised the murder of a master by his servant, of a husband by his wife, or of a bishop by a clergyman. Petty treason ceased to be a distinct offence from murder in 1828, and consequently high treason is today often referred to simply as treason.
Considered to be the most serious of offences (more than murder or other felonies), high treason was often met with extraordinary punishment, because it threatened the safety of the state. Hanging, drawing and quartering was the usual punishment until the 19th century. Subsequent to the Judgement of Death Act 1823, it was the only crime other than murder for which a death sentence was mandatory. Since the Crime and Disorder Act 1998 became law, the maximum sentence for treason in the UK has been life imprisonment."Treason: The Facts", The Guardian, 17 October 2014 (retrieved 28 August 2017).
The last treason trial was that of William Joyce, "Lord Haw-Haw", who was executed by hanging in 1946. The last conviction under a Treason Act was of Jaswant Singh Chail in 2023, who was charged with an offence relating to a plot to kill Queen Elizabeth II. At the time of the trial his offences were referred to in the media as simply "treason", but the statute he was charged under describes it as "a high misdemeanour".Treason Act 1842, section 2 at the National Archives website (retrieved 6 October 2023)
Offences High treason today consists of: Treason Act 1351 (as amended – last amended by the Succession to the Crown Act 2013): compassing the death of the sovereign, or of the king's wife (but not a ruling queen's husband), or the sovereign's eldest child and heir violating the king's wife, or the sovereign's eldest unmarried daughter, or the sovereign's eldest son's wife (only if the eldest son is also heir to the throne) levying war against the sovereign in the realm adhering to the sovereign's enemies, giving them aid and comfort, in the realm or elsewhere killing the King's Chancellor, Treasurer (an office long in commission) or Justices Treason Act 1702 and Treason Act (Ireland) 1703: attempting to hinder the succession to the throne under the Bill of Rights 1689 and the Act of Settlement 1701 Treason Act 1708: killing the Lords of Session or Lords of Justiciary in Scotland (in Scots law only) counterfeiting the Great Seal of Scotland
For detail about the offences created by the 1351 Act, see .
Northern Ireland In addition to the acts of 1351 and 1703, two additional acts passed by the old Parliament of Ireland apply to Northern Ireland alone. The following is also treason: Treason Act (Ireland) 1537: attempting bodily harm to the king, queen, or their heirs apparent attempting to deprive them of their title publishing that the sovereign is a heretic, tyrant, infidel or usurper of the Crown rebelliously withholding from the sovereign his fortresses, ships, artillery etc. Crown of Ireland Act 1542: doing anything to endanger the sovereign's person doing anything which might disturb or interrupt the sovereign's possession of the Crown Although the Act of Supremacy (Ireland) 1560 (2 Eliz. 1 c. 1 (I)) is still in force, it is no longer treason to contravene it.The Religious Disabilities Act 1846 (9 & 10 Vict. c. 59), s. 1
Treason felony In addition to the crime of treason, the Treason Felony Act 1848 (still in force today) created a new offence known as treason felony, with a maximum sentence of life imprisonment instead of death (but today, due to the abolition of the death penalty, the maximum penalty both for high treason and treason felony is the same—life imprisonment). Under the traditional categorisation of offences into treason, felonies, and misdemeanours, treason felony was merely another form of felony. Several categories of treason which had been introduced by the Sedition Act 1661 were reduced to felonies. While the common law offences of misprision and compounding were abolished in respect of felonies (including treason felony) by the Criminal Law Act 1967, which abolished the distinction between misdemeanour and felony, misprision of treason and compounding treason are still offences under the common law.
It is treason felony to "compass, imagine, invent, devise, or intend":
to deprive the sovereign of the Crown, to levy war against the sovereign "in order by force or constraint to compel her to change her measures or counsels, or in order to put any force or constraint upon or in order to intimidate or overawe both Houses or either House of Parliament", or to "move or stir" any foreigner to invade the United Kingdom or any other country belonging to the sovereign.
Treason Act 1842 Section 2 of the Treason Act 1842 creates offences of assaulting or alarming the Sovereign or having a weapon in the Sovereign's presence. This is described as "a high misdemeanour" and has a maximum sentence of seven years.Section 2 of the Treason Act 1842 at the National Archives website
History: England and Wales In England, there was no clear common law definition of treason; it was for the king and his judges to determine if an offence constituted treason. Thus, the process became open to abuse, and decisions were often arbitrary. For instance, during the reign of Edward III, a knight was convicted of treason because he assaulted one of the king's subjects and held him for a ransom of £90. It was only in 1351 that Parliament passed legislation on the subject of treason. Under the Treason Act 1351, or "Statute of Treasons", which distinguished between high and petty treason, several distinct offences constitute high treason; most of them continue to do so, while those relating to forgery have been relegated to ordinary offences.Coinage Act 1832 (2 & 3 Will. 4. c. 34) and Forgery Act 1861 (both repealed)
First, it was high treason to "compass or imagine the death of our Lord the King, of our Lady his Queen, or of their eldest son and heir." The terms "compass or imagine" indicate the premeditation of a murder; it would not be high treason to accidentally kill the sovereign or any other member of the royal family (though someone could be charged with manslaughter). However it has also been held to include rebelling against or trying to overthrow the monarch, as experience has shown that this normally involves the monarch's death. The terms of this provision have been held to include both male and female sovereigns, but only the spouses of male sovereigns. It is not sufficient to merely allege that an individual is guilty of high treason because of his thoughts or imaginations; there must be an overt act indicating the plot.Kenny, C. Outlines of Criminal Law (Cambridge University Press, 1936), 15th edition, p. 308
A second form of high treason defined by the Treason Act 1351 was having sexual intercourse with "the King's companion, or the King's eldest daughter unmarried, or the wife of the King's eldest son and heir." If the intercourse is not consensual, only the rapist is liable, but if it is consensual, then both parties are liable. Anne Boleyn and Catherine Howard, wives of Henry VIII, were found guilty of treason for this reason. The jurist Sir William Blackstone writes that "the plain intention of this law is to guard the Blood Royal from any suspicion of bastardy, whereby the succession to the Crown might be rendered dubious." Thus, only women are covered in the statute; it is not, for example, high treason to rape a queen regnant's husband. Similarly, it is not high treason to rape a widow of the sovereign or of the heir apparent.
In 1994, the book Princess in Love by Anna Pasternak, for which James Hewitt was a major source, alleged that Hewitt had a five-year affair with Diana, Princess of Wales from 1986 to 1991."Diss and Tell". People. 17 October 1994. Diana confirmed the affair in her 1995 Panorama interview. As she was then the wife of the Prince of Wales, heir to the throne, this fitted the definition of high treason, and a national newspaper briefly attempted to have Hewitt prosecuted for what was then still a capital offence.The New York Times
It is high treason "if a man do levy war against our Lord the King in his realm" or "if a man be adherent to the King's enemies in his realm, giving to them aid and comfort in the realm or elsewhere." Conspiracy to levy war or aid the sovereign's enemies do not amount to this kind of treason, though it may be encompassing the Sovereign's death. In modern times only these kinds of treason have actually been prosecuted (during the World Wars and the Easter Rising"On This Day: Sir Roger Casement sentenced to death" 29 June 2022, IrishCentral.com (retrieved 23 August 2022).).
The Treason Act 1351 made it high treason to "slay the Chancellor, Treasurer, or the King's justices of the one bench or the other, justices in eyre, or justices of assize, and all other justices assigned to hear and determine, being in their places doing their offices." The office of Lord High Treasurer has been in commission since 1714 and as such, it is not currently possible to commit treason in respect of the holder of that office.
The last types of high treason defined by the Treason Act 1351 were the forgery of the Great Seal or Privy Seal, the counterfeiting of English (later British) money and the importing of money known to be counterfeit. These offences, however, were reduced to felonies rather than high treasons by the Forgery Act 1861 and Coinage Act 1832 (2 & 3 Will. 4. c. 34) respectively.
Finally, the Treason Act 1351 specified that the listing of offences was meant to be exhaustive. Only Parliament, not the courts, could add to the list. It provided that if "other like cases of treason may happen in time to come, which cannot be thought of nor declared at present", the court may refer the matter to the King and Parliament, which could then determine the matter by passage of an act. (See constructive treason.)
After the passage of the Treason Act 1351, several other offences were deemed to comprise high treason by act of Parliament. Parliament seemed especially unrestrained during the reign of Edward III's successor, Richard II. Numerous new offences—including intending to kill the Sovereign (even without an overt act demonstrating such intent) and killing an ambassador—were declared treasonable by the Treason Act 1397 (21 Ric. 2. c. 12). Richard II, however, was deposed; his successor, Henry IV, rescinded the legislation and restored the standard of Edward III.
In 1495 Poynings' Law extended English law to cover Ireland.