As it turns out, there is no need to worry. Freedman has brought along his own photogenic props: a clutch of wallets and a wedge of fake banknotes which turn out to be a neat marketing device, with a picture of Freedman in place of the Queen headed with the legends “The Man of Steal”, and “International Comedy Pickpocket”.

Freedman takes pickpocketing very seriously. His interest in magic and sleight-of-hand began at school when he stole his friends’ ties at lunch. After a career as a chartered surveyor he returned to the business professionally and is now in charge of Dynamic FX, a company which supplies magicians for live events and TV and film consultancy. As well as Oliver Twist, he has advised on the TV series Hustle and Edward Norton’s forthcoming film The Illusionist.

As Freedman poses for photographs on the spot by London Bridge where Nancy’s body is discovered in Dickens’s novel, he talks about his time on the set of Oliver Twist. He was flown over to Prague to meet Polanski and “stole his watch — job done.” His company then choreographed the pickpocketing sequences here and returned to Prague several times over the course of a month to train the actors, going over the tricks “thousands of times” .

“Roman delayed the shooting of key scenes to get them up to speed, because he wanted them to look like they’ve been doing it for years. Harry Eden (who plays the Artful Dodger) was a natural. You need confidence, and children are more fearless. They stole from the crew, and from me. I felt like Fagin myself.”

After the photos. Freedman gives me a mini masterclass in thievery. “It’s 5 percent about how, and 95 percent about why,”, he says. “It’s about making people notice certain things. Some magicians call it misdirection, but I call it direction — directing people towards what you want them to see. Sitting next to Roman on the set I realized that we’re in the same business: perception management.”

Freedman gives me his jacket to put on. In the inside pockets are two wallets and two pens. Keeping eye contact, he asks what I have in my jeans pockets. I show him some keys and replace them. During those few seconds, he nicks the wallets and pens. As I’m reacting to this first loss, he manages to extract the keys out of my backpocket. I don’t see a thing.

It’s rather embarrassing. I knew what he was going to do and yet he still managed to fleece me. I don’t even have the excuse of a natural distraction, which, Freedman says, is what pickpockets look out for. “At Westminster Tube station,” he says, “the first thing people do when they come out is look at Big Ben.” And, of course, thieves love the posters in the Tube that warn people to safeguard their belongings “because people show you where their things are when they pat them.”

Knowing the tricks of the trade does have a down side. “After a while, your sense of wonder goes. Film-makers are the same. When I saw Oliver Twist for the first time, I couldn’t disassociate. Everyone else was seeing the film in Dickensian London, but I was seeing the set in Prague. The magic — the thing that got you hooked in the first place — is what you have to give up.”

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