Samuel Youd, the British science-fiction author who wrote classics such as The Tripods and The Death of Grass under the pseudonym John Christopher, has died aged 89. His other pseudonyms included Stanley Winchester, Hilary Ford and William Vine.

After serving in the Second World War, Samuel Youd began his professional career as a writer thanks to a scholarship from the Rockerfeller Foundation. Adopting the pen-name John Christopher, he scored a notable success with his 1956 novel The Death of Grass, about a virus that kills all forms of grass.

In the 1960s he started writing for the youth market, and in 1967 The White Mountains was published. This was the first instalment in The Tripods, which followed the adventures of a group of teenagers attempting to organise resistance to huge robotic alien invaders. Three more novels followed in the series, which was adapted by the BBC into a successful TV series in the 1980s.

Another hit series followed in 1970 with the Sword of the Spirits trilogy, and under his various pseudonyms Samuel Youd was increasingly prolific throughout the 1970s. He slowed down in later years and his last novel was 2003’s Bad Dream, published under the John Christopher name.