A man has been sentenced to seven years jail for killing a friend who was wearing what they thought was a bulletproof vest. Lorry driver Ian Catley fired a shotgun at Philip Harper in a farmer’s field near Melbourn, Cambridgeshire, June last year because Harper had asked him to help him test out his new purchase.

The plastic-lined garment instead funnelled the shotgun spray into the centre of his chest, severing an artery, and the 46-year-old died almost instantly.

His killer initially told police he had been aiming at a pigeon, but Southwark crown court heard on Friday that Catley quickly admitted he had agreed to shoot his friend at close range.

Catley, 40, of Melbourn, pleaded guilty to manslaughter last November. His barrister, Mark McDonald, had argued that the killing was the result of a reckless act to which Harper had consented. He had visited a military surplus store the previous day and was “very keen” to test the garment described by prosecutor Martin Mulgrew as a “protective” vest.

The court heard that after leaving Rugby Trading International Ltd with his new vest, Harper had asked a friend – James Hill – to help him test it out, but that Hill had flatly refused.

“[Harper] was very proud of it. He’d gone to the pub that evening wearing that vest and indeed a Swat cap,” McDonald said.

Harper had a drink or two and asked around, McDonald said, and his client fatefully agreed.

He said Catley had nightmares and woke each morning remembering what he had done.

“He’s lost his friend, a close friend, and he did it because of his own stupidity and his recklessness,” McDonald said.

“You shot Mr Harper at a distance of less than 20 feet, causing him catastrophic injuries and immediate death,” Judge Jeffrey Pegden QC told Catley at sentencing. “You then, straight away, took him to hospital but tragically, nothing could be done to save his life.”

Catley stared straight ahead in the dock as the sentence came down, while his elderly mother appeared to fight back tears in the public gallery.

“Your remorse is complete and genuine,” the judge said. “You recognise the magnitude of your actions and I have no doubt that the effects of killing your good friend will last with you for the rest of your life.”

The judge added that the victim seemed to have been an enthusiastic participant in the tragic shooting, saying: “For reasons which will never be known, Mr Harper was extremely eager to test the effectiveness of that vest whilst he wore it.”

But he added: “The risk of death or serious injury to Harper must in my judgment have been absolutely obvious”, he said, and Catley had “manifestly breached” the obligations and duties that came with holding a gun licence.

Catley will serve up to half his seven-year sentence, and the judge ordered that his gun be forfeited and destroyed.