Her acknowledged love affairs were some of the great sex scandals of their day and the rumours were even more lurid.

But few of the stories about Princess Margaret are as murky as claims to be made in a new film – that MI5 staged a London bank robbery as a ruse to eliminate sexually compromising photographs of her on the Caribbean island of Mustique.

The Bank Job, clips of which were shown last week at the Cannes film festival, tells the story of the notorious Baker Street robbery in 1971. It will be released next year and stars Jason Statham, who played the lead role in the gangster film Lock, Stock and Two Smoking Barrels.

In the film, which purports to be based on fact, the photographs are placed in the bank for safe-keeping by Michael X, a well-known criminal originally from the Caribbean.

“What happens in the film is that the raid on Lloyds is set up by MI5,” said Steven Chasman, the producer. “They knew that a box owned by Michael X with those pictures was inside the bank vaults.”

MI5 then got some of its minor gangland contacts to initiate the raid. The contacts in turn tipped off criminals they knew that the Lloyds Bank in Baker Street would be easy to break into and had a lot of money to steal.

The writers of the film – the veteran team of Dick Clement and Ian La Frenais – spoke to at least six people directly involved in some way with the robbery. The writers declined to name their sources, but said that several of them separately claimed the raid was aimed at getting hold of the photographs.

At the time of the robbery, Margaret’s marriage to the Earl of Snowdon was in its final stages. As a single woman in the 1950s, she had already created a scandal when she began an affair with Peter Townsend while he was still married. During her marriage she became close to Robin Douglas-Home, nephew of the former prime minister Lord Home. He shot himself in 1968.

The palace establishment was frequently worried that Margaret was moving in excessively racy circles and opening herself up to scandal. There was tittle-tattle about rumoured lovers – ranging from the actor Peter Sellers to the singer Dusty Springfield.

The gangster John Bindon also claimed to have been her lover.

The robbers got away with £500,000 (equivalent to £5m today), although it is not yet clear whether the film portrays the attempt to recover the photographs as successful. Four men were jailed in 1973 for the raid. Michael X was hanged for murder in Trinidad in 1975.

The film does not detail what exactly is in the photographs and Margaret is not referred to directly although Chasman said “we are pretty clear who we are talking about”.

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