 As most of the established production staff were working on other films at Ealing, many of Mackendrick's team were inexperienced.On what was supposed to be the first day of filming, Mackendrick threw away the script and had Mackenzie and MacPhail rewrite it over two days.For a box of cigars, Mackenzie was persuaded to add material to the script from his 1943 novel "Keep the Home Guard Turning".