Armed robber convicted of £40m diamond heist

An armed robber has been found guilty of taking part in Britain's biggest jewel heist, the £40m raid at the Graff Diamonds store in Mayfair. Aman Kassaye, 24, was convicted yesterday after nine days of jury deliberation.

He held a female shop assistant at gunpoint and forced her to empty cabinets full of some of the most expensive jewellery in Britain. He then fired shots when he and an accomplice were approached outside the store. The jury, which has previously heard that none of the 43 items of jewellery has been recovered, is still deliberating about its verdicts for six of Kassaye's co-defendants, all of whom deny charges relating to the robbery. The verdict on Kassaye was delivered yesterday morning at Woolwich Crown Court in south-east London. He was convicted of kidnap, conspiracy to rob and possessing a firearm. He was acquitted of a further gun possession charge. He showed no emotion and gave a thumbs up to his family in the public gallery as he was led away.

Earlier in the trial, which started in April, the jury was shown CCTV footage of Kassaye and his co-defendant Craig Calderwood, 27 – both of whom had been disguised by professional make-up artists – entering the store on London's New Bond Street at about 4.40pm on 6 August, 2009.

Once inside, they pulled guns on the staff and forced them to lie on the floor. One female shop assistant, Petra Ehnar, was taken hostage and forced into the street at gunpoint, before the robbers fled in a BMW. The jury heard that Kassaye and his accomplices then made an elaborate escape which involved using three getaway cars and trucks to block the roads behind them.

In his defence, Kassaye, who has previous convictions for drug possession and possessing an offensive weapon, claimed that he was not the man in the video and that a man named Omar had been made up to look like him.

In his evidence, Calderwood admitted taking part in the raid, but said he had been acting under duress as he had been told that he and his mother would be killed if he did not. He told the jury that underworld figures known as "Kev" and "the big boss" had planned the raid. The court was even told of a letter found in Calderwood's cell in which he apologised for his actions. It read: "I'm truly sorry for the crime I committed. The man you are going to see in the video, that's not me."

Calderwood's barrister Ian Bourne QC said his client was "press-ganged" into carrying out the raid. He said: "Those at the top and those who are in control of what is going on are able to remain detached, are seldom seen and are never caught."

Kassaye's barrister, Courtenay Griffiths QC, offered the court another suggestion: that the raid was an inside job and that staff knew it was going to happen. He put this to the store manager Martin Leggatt, in cross examination, who denied the allegation.

Craig Calderwood, 27, of no fixed address; Solomun Beyene, 25, of Marylebone, north-west London; Clinton Mogg, 43, of Bournemouth; Courtney Lawrence, 31, of Ladbroke Grove, west London; David Joseph, 23, of Elephant and Castle, south-east London; and Thomas Thomas, 45, of Kingston upon Thames, are all accused of conspiracy to rob. Calderwood is also charged with two counts of possessing a firearm. The jury will continue its deliberations on Monday.