sudden flow of wealth enabled Adams to retire from the civil service and become a full-time writer.

It also drove him into tax exile on the Isle of Man, although he later returned to his roots in southern England.

By the time Watership Down was published, he was already writing his second book Shardik, the novel he considered his best work.

Image copyright United Artists Image caption The Plague Dogs was an attack on animal experimentation

It is an epic tale of a bear who is a god in an imaginary world and who is abused by the humans in the story.

Shardik did not find favour among critics with some describing it as "preachy", a judgement with which Adams did not disagree.

His commitment to animal welfare was expressed in his third novel,The Plague Dogs, an outspoken attack on animal experimentation.

He admitted that his indignation about vivisection might have got the better of him but the book became another best-seller.

Charity president

He became president of the RSPCA but his attempts to persuade the charity to adopt a more campaigning stance did not find favour with some of the more conservative members of the ruling council.

He resigned just ahead of a vote which would have severely curtailed his presidential powers.

Despite his campaigning for animals he insisted he was not a sentimentalist.

He refused to condemn a decision to gas rabbits on the real Watership Down in 1998 after their burrows began undermining the hill.

"If I saw a rabbit in my garden I'd shoot it," he once said.

Image copyright Rex Features Image caption Adams