FANTASY author Sir Terry Pratchett, who wrote 40 books in the popular Discworld series, has died aged 66 after a long battle with Alzheimer's disease.

A long-time advocate of assisted suicide, Sir Terry often poked fun at death in his books and in a final tweet to the world he wrote a satirical comment from ‘beyond the grave’ which said: “At last, Sir Terry, we must walk together”.

His books which he described “as an antidote to bad fantasy” sold 85 million copies worldwide and were translated into 36 different languages.

The setting for Discworld, which was a flat planet floating through space on the back of a giant turtle, was imaginary but it often satirised aspects of modern life.

Later moving to Broad Chalke in 1993 he played an active part in community life, opening shops and visiting local schools.

He was never seen without the wide-brimmed hat he described as more urban cowboy than city gent, saying: “If I take it off, I’m just another bald-headed, bearded man”.

Born in the Buckinghamshire town of Beaconsfield in 1948, Terence David John Pratchett was an only child who described how he came to reading quite late in his childhood.

He left school at 17 taking a role as a trainee reporter for the Western Daily Press which he later said gave him confidence in his writing.

However he left journalism to take up a role working as a press officer for the Central Electricity Generating Board (CEGB) in 1980.

It was soon after the Three Mile Island nuclear accident in Pennsylvania and it was after a stressful day of insisting that there was no reason to be concerned about a leak at the Hinkley Point nuclear power station in Somerset, he went home and wrote one-third of his first book. “Writing”, he said, “is the most fun you can have with your clothes on.”

The first of Pratchett’s Discworld novels, The Colour of Magic, was published in 1983 but it wasn’t until his fourth book Mort came out in 1987 that he had the financial security to quit his job at CEGB.

His fantasy novels, despite being aimed at children, often drew parallels with the cultural and scientific topics of the day. But Pratchett always insisted that he had “no social agenda”.

He and his family moved to Broad Chalke in 1993, where they lived in a six-bedroom manor house.

It had an outhouse for writing and a tennis court he never used. He was always upright and operational by 9am so that he could stop for a bowl of muesli at 10am and feel as though he was taking a break from work, rather than bemoaning not having started.

His books generated adaptations for the stage, radio and television, with Salisbury amateur dramatic group Studio Theatre producing adaptations of Going Postal and Making Money.

Diagnosed with Alzheimer’s disease in 2007 he described his illness as an “embuggerance” and continued to make public appearances, never shying away from his condition.

In 2008 he walked to number 10 with then Salisbury MP Robert Key to ask for an increase in dementia research funding and donated £500,000 the Alzheimer’s Research Trust.

Despite his illness he continued to write and finished his final Discworld novel last summer, dictating his words to an assistant.

In 2009 he was “delighted, honoured and, needless to say, flabbergasted” to be given a knighthood for his services to literature.

Sir Terry Pratchett, OBE died on Thursday, March 12 in Broad Chalke surrounded by his family, with his cat sleeping soundly on his bed.