A soldier from the elite unit responsible for protecting the royal family has been jailed for three years after selling bullets to an undercover officer in a police sting.

Rajon Graham, 34, a lance sergeant in the 1st Battalion of the Coldstream Guards – recognisable by the distinctive red jackets and black bearskin hats – was dishonourably discharged from the British Army in October last year after pleading guilty to four counts of selling ammunition.

He was based at the Wellington Barracks near Buckingham Palace and tasked with carrying out state and ceremonial duties at the time of the offences between December 7, 2020 and January 28, 2021, Southwark Crown Court heard.

Graham sold a total of 300 9mm bullets, which he referred to as “sweets”, wrapped in Bacofoil sandwich bags, for £5,800 in cash to an officer posing as a serious criminal involved in the drugs trade.

The defendant intended there to be a high risk of death or serious harm because he was selling 300 live bullets to an individual he believed was involved in the dealing of drugs and had criminal associates who needed live ammunition in the context of the drugs trade

The ammunition was from a manufacturer who supplied the Coldstream Guards – the oldest continuous regiment in the Army, which carries out ceremonial duties at Buckingham Palace and Windsor Castle – but the Army claimed the bullets were not stolen from the military, the court heard.

However, Judge David Tomlinson, sentencing Graham, who was born in Jamaica, to a total of three years on Thursday said: “Your ability to obtain this ammunition must have been connected to your occupation.”

The judge praised married father-of-one Graham’s “exemplary” service “provided to this prodigious wing of our armed services” over eight years.

He added: “You believed that the person who paid you for this ammunition was an active criminal and someone you must or ought to have realised was part of an organised crime group.

“In fact, no harm was done because the individual you did this business with was an undercover police officer.”

The court heard Graham, who was responsible for the ceremonial kit used by the regiment, including swords and bearskins, boasted to the undercover officer, “D”, of his criminal network.

He took D inside Victoria Barracks, the Windsor base of the Coldstream Guards, during a meeting on December 17, 2020, and offered to show him live rifles in the armoury, but the officer refused because it was “too risky”.

Prosecutor Duncan Atkinson KC said: “The defendant intended there to be a high risk of death or serious harm because he was selling 300 live bullets to an individual he believed was involved in the dealing of drugs and had criminal associates who needed live ammunition in the context of the drugs trade.”

Graham was arrested alongside Warrant Officer Kirtland Gill, 42, who was due to become the first black regimental sergeant major in the Coldstream Guards.

He was cleared of plotting to sell ammunition with Graham after a trial last year after claiming he had “no knowledge” of the scheme and telling the jury his friend Graham set him up.

“He’s leading a double life,” he said. “I would even question if he’s mentally stable.”

Graham was arrested again just two weeks after he entered his guilty pleas for giving someone a revolver loaded with two live rounds at a party in Tottenham, north London, in December 2021, but not charged.

Austin Stoton, defending, said he had an “impeccable service record” but fell into “desolate times” after suffering depression following his return to the UK from a tour of Afghanistan in 2013.

“This was the beginning of this rather sad tale,” he said, telling the court his client was told by a Jamaican friend he could make money from selling ammunition.

“He realises that was a stupid, naive thing to do.”

Detective Constable Simon Dadgostar, from the Flying Squad, said: “The actions of Graham are simply shocking.

“Our detailed and protracted investigation highlighted the lengths he went to in order to hide his criminal activity.

“Graham was in a position of trust and power which he abused and now he will pay the price.

“The Met will continue to work hard in preventing firearms and ammunition making it onto London’s streets, and tackling all forms of violence.”