A trio of burglars crawled through a hole they smashed in the wall of a jewellers to steal £1.8 million of goods, police said.
Asian gold and diamond necklaces, bracelets, pendants and earrings were looted during the early-morning raid at Joyalukkas in Forest Gate, east London, the Metropolitan Police said.
Three men wearing gloves spent more than three hours inside the shop after using a sledgehammer and crowbar to make a hole in the wall at the rear, between 3am and 6.40am on Monday July 10.
Three other men watched the premises in Green Street from 5pm the previous day, while police believe another two men also acted as lookouts.
CCTV footage released by Scotland Yard shows two men inside the shop, one of whom wears a hoodie drawn up around his face and is sprawled on his front as he pulls jewellery out of drawers before stuffing it into a rucksack.
Detective Chief Inspector Andy Pallett, of Newham CID, said: "This was a meticulously planned and audacious raid on a jewellery shop with £1.8 million of items stolen.
"While we think it only took the suspects around 20 minutes to make the hole, it must have been noisy work and we would appeal for anyone who heard or saw anything suspicious to contact us."
Joyalukkas, one of a cluster of jewellers in Forest Gate, is part of an international chain which describes itself on its website as "the world's favourite jeweller".
Its ambassador is Bollywood actress Kajol Devgan, and it claims to have 10 million customers.
The thieves are believed to have escaped over a wall into a builders' yard behind the shop, making off in the direction of Plashet Road.
Some of the men are described as in their mid-30s, while one wore a distinctive hot pink hoodie, one a black coat and another a T-shirt and shorts.
No arrests have yet been made, the Met said.
The force is appealing for information from anyone who may have seen the men or has been offered jewellery for sale following the raid.
Anyone with information should contact Newham CID on 020 8217 5414 or Crimestoppers anonymously on 0800 555 111.