Thieves with sledgehammers broke into a jewellers in a south-west London shopping centre and then pelted police with some of the watches they had stolen as they tried to escape.
Items valued at £500,000 were taken from Fraser Hart Jewellers at the Bentall Centre in Kingston upon Thames.
One of the shop's windows was smashed and a security guard was threatened in the raid, at 0030 BST on Wednesday.
Four men have been arrested in connection with the raid.
The suspects escaped on three mopeds and two men are still being sought.
Series of raids
Two men were arrested in Sandy Lane in Sutton, south-west London, after one moped crashed.
A tip-off led to two others being held in Cecil Road, Wimbledon, south-west London, a few hours later.
The four men are aged 21, 23, 26 and 32.
A police helicopter was involved in the search and a large number of the luxury watches have now been found, police said.
The Met believes the men may be linked to a larger criminal gang responsible for several similar raids across London in recent months.
Goods valued at more than £4m have been taken from branches of Watches of Switzerland, Cartier, Dolce and Gabbana, De Beers and Tiffany and Co.