Scotland Yard appealed to the public tonight 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.
The biker was forced to abandon his gold-coloured Suzuki SV650 when it broke down just a short distance away in Berkeley Square.
Officers 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.
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 tomorrow.
Calderwood was accused of planning and executing the heist alongside Aman Kassaye, 25, convicted of kidnap, conspiracy to rob and possessing a firearm.
Detective Chief Inspector Pam Mace, of the Flying Squad, said: "The conviction of these men is a successful outcome of what was a fast-moving investigation.
"I'd like to pay tribute to all the witnesses for their courage in supporting this prosecution and to thank my team and everyone else who has worked tirelessly on this investigation.
"There remains an active ongoing investigation and we continue to appeal for information to trace the motorbike rider, and the whereabouts of the jewellery."
The high-stakes Graff robbery seized headlines around the world as details emerged of the audacious crime.
Two smartly dressed robbers used make-up to disguise their appearance and talk their way past security guards.
They held shop assistant Petra Ehnar at gunpoint, forcing her to stuff a bag with jewels during the two-minute raid.
She was then held hostage as the two men got into a blue BMW outside the store, shooting at a guard who tried to tackle them.
A total of four men have been convicted for their roles but none of the jewels have been recovered.
Beyene bought so-called dirty telephones and hired a van to use as a blocking vehicle. Mogg provided the London address used by the innocent make-up artist, who did not know about the planned raid.
Aman Kassaye, 25, used a professional make-up artist to disguise his appearance and a series of getaway cars to escape. Thomas Thomas, 46, of Kingston upon Thames drove some of the blocking vehicles after the heist.
Two other men accused of conspiracy to rob, Courtney Lawrence, 31, and David Joseph, 23, were cleared last week.
The heist dwarfed what is thought to be Britain's previous biggest jewellery robbery, a £23 million raid at the same store in 2003.
Two Serbians, part of the Pink Panther gang, held up staff with a revolver. One gang member was wrestled to the ground as he fled and was later jailed.
In 2007, jewellery worth up to £10 million was stolen from a branch of Graff Diamonds in London's Sloane Street by two men posing as customers.