When I was about five or six years old, my best friend, from whom I was inseparable, contracted polio and was paralysed from the waist down. My parents were ‘paralysed with fear’, to quote the title of this book, that I would be next.

I was not; and I am glad to say that my parents behaved towards my best friend with generosity. We remained inseparable for a number of years afterwards. His mother, a Christian Scientist, did not believe in the reality of illness, which, though absurd, turned out to be the best for him, as it encouraged him to disregard his disability to an astonishing extent. A few years later his mother contracted breast cancer, for which she chose to receive no treatment. I remember her close to death, in a room darkened by closed plush curtains; whether any treatment would have prolonged her life I do not know. But between them, polio and cancer taught me early that human fate and desert are not one and the same.

Polio was also important in Gareth Williams’s childhood. He was a guinea pig in a trial of the first effective oral vaccine against polio. This vaccine turned out to be defective because the live, attenuated virus used in it turned out in some cases to recover its virulence during its