A silver Vauxhall Vectra Estate smashed through security shutters at the exclusive Mappin & Webb store in London's posh West End at 1am this morning.
Four men were seen fleeing the shop with the loot before hopping on to mopeds and speeding off towards Piccadily Circus.
Cops are linking the raid to an earlier attack on the Regent Street shop - jeweller to the Queen and Prince Charles.
Just five days ago thieves fled Mappin & Webb on mopeds with a £30k haul after smashing the stores windows with hammers in a brazen 9pm attack.
They had ridden off in the direction of Oxford Street.
Yesterday the shop floor was covered in shattered glass and smashed display cabinets lay empty after being robbed of their contents again.
Police believe the S-reg Vauxhall used to barge through the shopfront was stolen.
A Scotland Yard spokesman said: "Police were alerted at 1.11am to a burglary at a jeweller in Regent Street.
"An S-reg Vauxhall Vectra Estate was driven through the front door and into the shop-floor of the premises."
Last night's raid is at least the fourth on the upmarket store in the past two years.
Moses Preddie, 16 - the younger brother of Damilola Taylor's killers - was jailed in May after targeting the shop.
His gang tried to escape along Whitehall in a van and were arrested at gunpoint by Downing Street cops.
Staff at Mappin & Webb will start assessing the damage caused last night as police hold urgent talks with bosses over security at the branch.
Westminster Burglary Squad appealed for witnesses to the latest raid. They can call 020 7321 8731 or Crimestoppers anonymously on 0800 555111.
.