I'd never seen or heard of Cloudburst prior to the recent showing on TCM. It's quite a good little film - well directed by Searle, whose work I don't know at all, with a top-notch score by Frank Spencer, a composer I also don't know. Preston is very good, as are the rest of the players, especially the actor who plays the Inspector. The storytelling is compelling, and there's a surprising complexity in Preston's character. Leo Marks, from whose play this was taken, was a fascinating writer and person - as one of the others points out, he really did work as a decoder during the war - and this isn't the only film he wrote where the central character is a decoder - he also wrote Sebastian, in which Dirk Bogarde plays a decoder. And, of course, Marks gave us the brilliant script to Michael Powell's Peeping Tom.

Worth catching if you can find it.