A man has been charged under the treason act after allegedly breaking onto the grounds of Windsor Castle while armed with a crossbow on Christmas Day last year.
The Metropolitan Police's Counter Terrorism Command said 20-year-old Jaswant Singh Chail, from Southampton, was also charged with threats to kill and possession of an offensive weapon.
The Queen was at Windsor Castle during the incident, celebrating Christmas alongside her son, Prince Charles, his wife Camilla, and other close family members.
Police said Mr Chail was arrested at around 830am and had been stopped "within moments" of entering the grounds, and did not enter any buildings on the property.
"The CPS has authorised the Metropolitan Police to charge Jaswant Singh Chail with offences after he was arrested in the grounds of Windsor Castle on 25 December 2021 carrying a crossbow," Nick Price, Head of the Crown Prosecution Service's Special Crime and Counter Terrorism Division, said in a statement.
"Mr Chail, 20, has been charged with making threats to kill, possession of an offensive weapon, and an offence under the 1842 Treason Act.
"The Crown Prosecution Service reminds all concerned that criminal proceedings against Mr Chail are active and that he has the right to a fair trial."
Mr Chail is set to appear at Westminster Magistrates' Court on August 17.
The most serious security breach during the Queen's reign happened in 1982, when an intruder climbed a wall using a drainpipe to enter Buckingham Palace and wandered into her bedroom in the royal apartments, where she was in bed.
Under the 1842 Treason Act it is an offence to assault the Queen or have a firearm or offensive weapon in her presence with intent to injure or alarm her.
In 1981, Marcus Sarjeant was sentenced to five years' imprisonment under this section of the treason act after pleading guilty to firing blank shots at the Queen when she was riding down The Mall in London for Trooping the Colour.
The last person to be convicted under the separate and more serious 1351 Treason Act was William Joyce, also known as Lord Haw Haw, who collaborated with Germany during the Second World War and was hanged in 1946.
