Alan M. Turing

This is the centenary edition of the life of Alan Turing written by his mother, with a new foreword and a revealing memoir by his brother. Turing's personality and genius comes across very clearly in these pages, as does his eccentricity - apparent in the number of anecdotes contributed by his friends. He first showed his mathematical ability at Sherborne, using a combination of intuition and ingenuity. In a mathematics prize he was asked, what is the locus of so-and-so, and his answer was that the locus is such and such; this was correct, but the examiners had expected a page and a half of proof. When asked why he had shown no proof, he said that it had not been asked for, but immediately saw it and wrote it down. On another occasion he produced an immediate formula on the lighting of a certain hall, and said he would send the proof in a few days. His mother gives a vivid impression of his characteristics, one of which was taking enormous trouble about finding gifts for people and also being very good with children.

While working during the war on code breaking at Bletchley, he had a bicycle whose chain repeatedly came off (he was in fact a very fine athlete). Rather than take it elsewhere for repair, he worked out how many revolutions of the pedals it was before the chain came off; then he fixed a counter on the bicycle to warn of approaching trouble, following which he discovered the mathematical relation between the number of pedal revolutions, links in the chain and spokes in the wheel. This showed that the chain came off when a slightly damaged link came in contact with a bent spoke - he duly straightened the spoke and had no more trouble. The memoir describes the background of his extraordinary contributions to computer science, mathematics, artificial intelligence and computational biology - and there are two essays on computing machinery and the theory of morphogenesis. He was elected a Fellow of the Royal Society before he was 40. His brother gives an altogether less flattering portrait, revealing that Alan in fact loathed his mother and had been a practising homosexual since his teens - at the time this was illegal, and he was even given oestrogen injections to try to modify his sex drive. It seems clear that an episode involving a burglary from his house led to the public revelation of his sexual preference and indirectly to his suicide. Since his death, his reputation has only grown, which makes this book all the more interesting reading.