Fantasy author Terry Pratchett, creator of the Discworld series of novels, has passed away at the age of 66.

Pratchett had been diagnosed with early-onset Alzheimer's disease in 2007, but remained a public figure. He campaigned for better funding for Alzheimer’s research, and also fronted BBC documentaries about living with disease, and his support of assisted suicide.

He was better known for his Discworld novels, a comic fantasy set on a world of magic and wizards that took place on giant disc on the back of turtle swimming through space. Since publishing the first book The Colour Of Magic in 1983, he wrote 40 novels in the series, which also spun-off into graphic novels, sciences books, radio, television and video games. His other well-known work included his children’s novels, such as Only You Can Save Mankind, and Good Omens, his collaboration with comic book writer Neil Gaiman.

His official Twitter account announced the news beautifully: