Before the pop excesses of Vox Lux, Brady Corbet’s debut feature explored the private life of a different kind of public figure. The Childhood of a Leader has a tricky concept to explain; it’s about the childhood of a man who will one day be a dictator, and is only named at the end of the film. Until then, the audience is given various clues and left to stew; we see The Boy (Tom Sweet) and his family round about the signing of the Treaty of Versailles in 1919. Could it be Hitler, or Mussolini? Before anyone scampers off to google it, The Boy is eventually named as Prescott, but who is Prescott meant to represent? Corbet’s film is slow and stately, with Liam Cunningham and Bernice Bejo as the boy’s parents and Robert Pattinson contributing a small but significant cameo. Corbet’s film is frustrating, but also immersive and rewarding; whatever it means, and the jury is out for now, it’s engrossing and serious work.