Why exactly was Christopher Nolan lobbying Warner Bros to release his new film Tenet to theatres in the middle of a pandemic, when cinemas around the world are operating at a sharply reduced capacity, if not entirely closed? That’s a conundrum only rivalled in convolution by the film’s plot. Nolan still got it done, and the film is the first blockbuster to reach the silver screens since March. But for all the confidence the Dunkirk director seems to have in his most recent work, there is little in the 150-minute film to back it up.