The incident at the Earl of Lonsdale, which was caught on TV and is reminiscent of a scene in BBC comedy Only Fools and Horses, involved a man crashing through a pub garden door, distracting the victim and other customers while another man appears unnoticed to nab the bag.
The victim, an antiques dealer, claimed the bag contained expensive jewellery, and police are studying the footage.
'We were so careful'
The victim told the Evening Standard: “We were all keeping an eye on each other’s bags, we’re always so careful, but when someone falls through a gate like that you can’t help but turn around.
“It was only a few seconds we were looking away but that’s all they needed.
“From the footage it looks like the man who took my bag was on a hands-free phone and there was a signal so he knew exactly when to strike.
“They are clearly professionals. I hope there is a chance I can get some of the jewellery back but more than anything I want these men caught so no one else is a victim.
“I make a living but the margins are small and this makes insurance out of the question. I’ve been quoted £9,000 a year.”
The theft took place around 2.30pm on Saturday August 20.
Both men have been described by Metropolitan Police as being of Middle Eastern appearance and aged around 40. The man who fell in the gate wore a black T-shirt, black trousers and black shoes and was carrying a brown rucksack.
The other suspect was wearing a light polo top, blue denim jeans and dark shoes and a dark cap.