Every film critic is asked: "What is your favourite film of all time?" And every critic, in spite of a preliminary sigh of protest, is secretly delighted to provide the answer. Ask a critic for his top 10 films and he will provide a list off the top of his head. Ask the same question 10 minutes later and he will provide a different list. This is the nature of the passion. And Alex Walker, my fallen comrade, was nothing if not passionate about films.