Sir William, one of the most powerful and original British post-war writers, was working on a new novel when he died at his home in Cornwall. He was awarded the Nobel in 1983 and the Booker Prize for his novel Rites of Passage in 1980. He was knighted eight years later.
But he will be best remembered for his first book, Lord of the Flies, which was rejected by 15 publishers before being published by Faber & Faber in 1954 and became a world classic.
Born in Cornwall, he worked in theatre companies before becoming a teacher. During the war he served in the Royal Navy.
Sir William had been at a party in his honour on Friday night and is believed to have died of a heart attack in the early hours at his home, Tullimaar, in Perranarworthal, near Falmouth, where he moved from Salisbury about 10 years ago.
Charles Monteith, who became Sir William's publisher after he discovered Lord of the Flies, said: 'He was one of the greatest writers I have known, he was also a warm, affectionate and very close friend.' He could also be moody.
'He had immense originality and a powerful imagination. He took enormous pains with his writing.'
Appreciation, page 3