Scotland Yard detectives have asked the public to help them trace a motorcyclist suspected of making off with the £40 million Graff jewellery haul.
The accomplice was passed a black plastic bin bag containing the gems moments after the record heist at the prestigious Mayfair store.
He was part of a sophisticated plan including blocking vehicles and numerous changes of getaway car to help the robbers escape. But the biker was forced to abandon his gold-coloured Suzuki SV650 when it broke down just a short distance away in Berkeley Square.
Officers scoured hundreds of hours of CCTV in a bid to trace his escape route through central London. They dubbed the mystery man "The Stig", after the Top Gear racing driver, because he did not remove his helmet. But they lost track of him after he walked into the 16-hectare green space of Green Park, a short distance from Buckingham Palace.
A reward of up to £1 million remains on offer for information leading to the recovery of the remarkable haul of 43 pieces.
Detectives also continue to hunt a suspected "Mr Big" who co-ordinated the raid from a distance.
The appeal for help came after a jury found two more men guilty of taking part in the robbery on August 6 last year.
Solomun Beyene, 25, of Marylebone, north-west London, and Clinton Mogg, 43, of Bournemouth, were convicted of conspiracy to rob at Woolwich Crown Court.
After 16 days of deliberation the jury was unable to reach a verdict on Craig Calderwood. A decision on a retrial will be made at the court on Wednesday.
Calderwood was accused of planning and executing the heist alongside Aman Kassaye, 25, convicted of kidnap, conspiracy to rob and possessing a firearm.
