If you are going to shoplift a $3,000 designer dress successfully, it pays to do your research, was the moral of Jeff Wall’s talk in London last week. Ditto if you are going to photograph a felon red-handed. The woman who inspired the artist Jeff Wall to create Changing Room (2014) can’t be faulted on her planning. She went into the fitting room with two of the same Bottega Veneta dresses to try on and she wore a thin silk dress so that she could easily slip it over the dress she was going to pilfer. Plus she was wearing the right accessories to look like she belonged in Barneys. “You have to have the right bag and very good shoes,” Wall said at the press preview of his solo show at Marian Goodman Gallery in London. (Meanwhile, Wall’s work is shown concurrently in the gallery’s New York space). In an off-the-cuff masterclass into shoplifting like a pro, he sounded like a store detective who had seen it all before. In the would-be felon’s luxury bag there was probably an iphone, he pointed out, so when she headed for the store’s exit wearing headphones, the volume turned up high, she had a ready-made excuse for not responding right away. Wall said the work and others in the show (until 19 December) are all “near documentary”. They are based, he said, on something he observed and feature a real place, only not necessarily the same place. The recreation is painstaking: it took 1,000 takes before he captured the right one of the African-print dress slipping over the woman’s head and shoulders to conceal the designer dress beneath. “Don’t try this yourself,” he said, in a characteristically deadpan way.