'There is an assassin set up to kill you': Chilling words of 17-year-old who fired six blank shots at the Queen during Trooping the Colour in 1981 after sending warning to letter to Palace

• Marcus Sarjeant had written a note warning the Queen not to attend ceremony 

Due to his ongoing cancer treatment, His Majesty will not be appearing on horseback for Trooping the Colour today. 

Instead, he is set to watch proceedings from a relatively stress-free position in a carriage before making the traditional appearance on the Buckingham Palace balcony.

But back in June 1981, Trooping ended up particularly stressful for Charles's mother the Queen - when 17-year-old Marcus Sarjeant fired six blank shots at her.

Her Majesty was riding her beloved horse Burmese down The Mall when the shots rang out, terrifying her steed. 

Showing her poise and coolness under pressure, the Queen calmed her horse and continued with her duties as Sarjeant was tackled by a soldier and then arrested. 

Sarjeant had sent a letter to Buckingham Palace before the attack that chillingly read: 'Your Majesty. Don't go to the Trooping the Colour ceremony because there is an assassin set up to kill you, waiting just outside the palace.'

However, the note arrived three days after the incident.

Sarjeant allegedly told Lance -Corporal Alex Galloway, the soldier who subdued him: 'I wanted to be famous. I wanted to be a somebody.' 

He was later jailed for five years under the 1842 Treason Act, which was introduced after two men made attempts on the life of Queen Victoria. 

Lance-Corporal Galloway told the Mail after the incident: 'My only thought was to save the Queen's life.

'I thought it was a real gun and dived across the barrier into the crowd and grabbed him.

'I took him by the hair and pulled him into the Mall. Within seconds the police arrived and took him away.' 

During police questioning after his arrest, Sarjeant claimed he had been inspired by the recent assassination attempts against US President Ronald Reagan and Pope John Paul II, and the murder John Lennon a year earlier. 

Sarjeant had previously made attempts to join the police and fire services and had also tried to join the Royal Marines. 

He also enlisted in the Army but left after only two days of induction.

He became involved in the anti-Royalist movement and bought two imitation Colt Python revolvers for £66.90. 

Both weapons were only capable of firing blanks, but Sarjeant had also tried and failed to get live ammunition for his father's handgun.

Sarjeant's grandmother Sylvia told the Mail before his conviction: 'I love the Royal Family - every one of them, especially the Queen and the Queen Mother, and I am heartbroken that my grandson should be charged with something like this.'  

While serving his three-year prison sentence, he reportedly wrote to the Queen to apologise but did not receive a reply. 

She did not let the 1981 incident change any of her plans - she was back on her horse for Trooping the following year.