A teenager named Marcus Sarjeant became the last person to date to be convicted under the Treason Act of 1842, after he fired a replica gun at the Queen on this day in 1981.

The 17-year-old fired six blanks in quick succession in the Queen’s direction, as she turned from The Mall into Horse Guards Road en route to the annual Trooping the Colour ceremony.  He was quickly overpowered by two Guardsmen, a police officer and a St John’s Ambulance volunteer.

The Queen, who had left Buckingham Palace 15 minutes earlier on her horse Burmese, was visibly startled by the shots, but regained her composure and brought the horse under control, before continuing on her route as her ceremonial escort closed ranks around her.

After the completion of the ceremony on Horse Guards Parade, she returned to the Palace by the same route under the close guard of her escort and security services.

[Read more: March 20, 1974 - Shots fired on The Mall as Princess Anne kidnap attempt is foiled]

Sarjeant, a former Air Training Cadet from Folkestone, Kent, had joined the Royal Marines a year earlier after leaving school, but had quit within three months, claiming he had been bullied. He had then tried to join the army, but left after just two days of an induction.

Unemployed at the time of the incident, he was said to be an anti-royalist, but when asked about the motivation behind his actions, he reportedly told his captors: “I wanted to be famous. I wanted to be a somebody.”

In September, Sarjeant became the first person to be tried under the 1842 Act since 1966, on a charge of wilfully discharging a gun “at or near Her Majesty the Queen…with the intent to alarm or distress Her Majesty."

Lord Chief Justice, Lord Lane sentenced Sarjeant to five years’ imprisonment, saying: “I have little doubt that if you had been able to obtain a live gun…you would have tried to murder Her Majesty.”