 Ivor Brown called his performance "a joy … a marvellous mixture of soap and vinegar".On the strength of this success Sim was cast in his first film, "The Riverside Murder" (1935), in the role of the earnest but dim Sergeant McKay.There followed a sequence of films, a mixture of comedies and detective stories, including "Wedding Group" (1936), in which Sim and his wife both appeared, he as a Scottish minister, she as the maid; Edgar Wallace's "The Squeaker" (1937), after a stage production of the same piece; "Alf's Button Afloat" (1938) with the Crazy Gang; also in 1938 he played a revengeful ex-con Soapy Marks in the Associated British Picture film "The Terror", and the "Inspector Hornleigh" series (1939–41), as the bumbling assistant of Gordon Harker.