JK Rowling to write new Harry Potter spin-offs

J.K. Rowling is to make her screenwriting debut by penning a series of Harry Potter spin-off films, putting her in line for a huge payday.

The first film will be called Fantastic Beasts and Where to Find Them and will be based on a textbook of the same name used by Harry and his classmates at their school, Hogwarts, Rowling announced.

Set in New York and featuring zoologist Newt Scamander - the author of Harry's textbook - it will be set in the magical world of the British boy wizard, but 70 years before the events at the core of the Potter novels.

The film comes two years after the final movie in the eight-part series spawned by her phenomenally successful novels.

"I always said that I would only revisit the wizarding world if I had an idea that I was really excited about and this is it," the 48-year-old Rowling said.

She pitched the idea to Warner Bros. herself after the US studio inquired about making Fantastic Beasts into a film.

"I thought it was a fun idea, but the idea of seeing Newt Scamander, the supposed author of Fantastic Beasts, realised by another writer was difficult," she wrote.

"As hardcore Harry Potter fans will know, I liked him so much that I even married his grandson, Rolf, to one of my favourite characters from the Harry Potter series, Luna Lovegood."

Rowling added: "Although it will be set in the worldwide community of witches and wizards where I was so happy for 17 years, Fantastic Beasts is neither a prequel nor a sequel to the Harry Potter series, but an extension of the wizarding world."

Rowling, who has sold more than 450 million copies of the Harry Potter books, has been busy since the final novel in the series was published in 2007.

She published her first novel for adults, The Casual Vacancy, last year to mixed reviews.

In July she was unmasked as the real author of critically acclaimed detective novel The Cuckoo's Calling, published under the nom de plume Robert Galbraith.

With an estimated fortune of US$885 million, the former single mother is the 156th richest person in Britain, according to the Sunday Times Rich List.

Warner Bros. will also act as worldwide distributor for the upcoming television miniseries adaptation of The Casual Vacancy, which begins production next year, it said.