John Christopher was the pen-name of Sam Youd, a celebrated and influential writer of science fiction. Youd was born in Huyton, Lancashire in 1922, and began his career as an author after serving in World War II.

Many of Youd's novels for adults and children are considered classics, including The Death of Grass, The Guardians, and the four books in his Tripods series, which were adapted successfully for television in the 1980s.

Sam Youd died in 2012, aged 89.