S teven Soderbergh has a certain superpower, not always bestowed on even the most important directors: a capacity to surprise. This is a restlessly productive film-maker, travelling light creatively, developing eclectic projects, shooting on digital, using intimate locations and getting the very best from an invariably classy cast. He has recently found himself in the UK and his latest London-set movie is terrifically exhilarating and funny, as bracing as a large vodka and tonic before lunch: fast, literate and funny with a key plot progression elliptically and unsentimentally managed. The Christophers is a movie about contemporary art and about what Alan Bennett in his play about Anthony Blunt called “a question of attribution”, and it puts new life and wit into the (perhaps) tiresome subject of movies on this subject: what has value and what does not.…