The magic of this film, I think, comes down to the writing of the dialogue by Wilder and his writing partner, Izzy Diamond. There are a number of conversations between Robert Stephens (Sherlock) and Colin Blakely (Watson) that are just like tiny symphonies. Every gag, every little annunciation or pause is poised perfectly and, watching it recently (it was a template of sorts for Stephen Moffat and me as we made our adaptation for the BBC) made me realise that Wilder and Diamond were among the best screenwriters in the world. They gently take the mickey out of Sherlock Holmes in the way that you can only do with something that you really adore. It's a fantastically melancholy film. The relationship between Sherlock and Watson is treated beautifully; Sherlock effectively falls in love with him in the film, but it's so desperately unspoken. There's an amazing scene where, to get out of a situation where a Russian ballerina wants Sherlock to father her child, he claims Watson and he are gay. Watson is outraged and, when he calms down, speaks of the women all over the world who could attest to his sexuality. He says to Sherlock, "You do too, don't you?" Holmes is silent, and Watson says, "Am I being presumptuous? There have been women, haven't there?" Holmes says, "The answer is yes – you are being presumptuous." Sensational.

Mark Gatiss's adaptation of HG Wells's The First Men in the Moon is out on DVD.