The ringleader of the £40 million Graff jewellery robbery in Mayfair was jailed for 23 years today.

Aman Kassaye, 25, was told he had inflicted “life-long trauma” on the store staff, especially shop assistant Petra Ehnar he had taken hostage.

Kassaye dragged her at gunpoint into the street on his way to a getaway car and also fired four shots at a security guard and members of the public.

Three other gang members, Clinton Mogg, 43, Thomas Thomas, 46, and Soloman Beyene, 25, were also jailed for 16 years each. They had all been convicted at Woolwich crown court of conspiracy to rob in August last year.

Kassaye was also found guilty of firearms offences and kidnapping Ms Ehnar. Judge Jeffrey Pegden told him: “At the time you succeeded in getting the jewellery and it has never been recovered but it’s the terror and the trauma the staff were put through and other members of the public that lie at the heart of this case.”

In only two minutes Kassaye and another armed robber stripped the New Bond Street store of 43 pieces of jewellery including a £3.5 million multi-coloured diamond necklace in Britain’s biggest gems raid.

They forced sales manager Martin Leggatt and his staff to the floor and held a gun at his head. Then they escaped in getaway cars provided by the other gang members who also blocked the traffic and any pursuing police officers.

Graff security guard Etan Azulay tried to rescue Ms Ehner and Kassaye shot at him from almost point blank range. He fired further shots when the getaway car crashed into a taxi in nearby Stafford Street as passer-by Robert French tried to intervene.

It was not certain that they were live rounds. Both Mr Azulay and Mr Rench were commended by the judge who awarded them £500 each for their bravery. The bag containing the jewels was passed to a motorcyclist who was last seen walking into Green Park.

Police are still hunting the crimelord who masterminded the raid and there is a £1 million reward for information leading to his arrest or the return of the gems.

The jury was unable to agree a verdict on Craig Calderwood, who is alleged to have been one of the armed robbers, and he faces a retrial.