"Professor Gerald Whitrow, who has died aged 87, wrote The Natural Philosophy of Time (1960) a tour de force that examined the subject from every side—mathematical, cosmological, historical, biological and psychological. ...As an opening for his talks, he would sometimes recount one of his favourite stories on time. It concerned the Russian poet Samuel Marshak, on a visit to London before 1914. Marshak's English was not too good and when he asked a man in the street "Please, what is time?", he received the surprised response, "But that's a big question. Why ask me?""