Her new novel, The Silkworm, is part of the Cormoran Strike series of detective novels, which she is writing under the pseudonym Robert Galbraith. Originally, Galbraith's 'real' identity as Rowling was meant to be kept a secret, but as she predicted - saying in 2003 that if she used a pen name, the press would "find out in seconds" - keen fans recognised her style in the first book in the series, The Cuckoo's Calling.

Speaking about hiding her identity at the event she said "I wanted to prove to myself I could get a book published on the merits of the book. A friend said, 'Why do you need that validation?' You probably have to be a writer to understand it... I wanted something that was just for me. While it lasted it was a lot of fun."

But Rowling has taken to her new 'personality' as Galbraith, running a Twitter account and a website 'for' him, and appearing at last night's event at the Theakstons Old Peculier Crime Writing Festival in Harrogate yesterday in a suit and tie, to give the impression of being a male crime writer.

She confirmed that the series would be "open-ended", in stark contrast to the Harry Potter series - which had always been set out to finish within seven books, despite its global success - and said that the story in The Silkworm was "probably the most complex plot I've ever written."

But its characters will continue to develop as the series goes on. She revealed "I think Robin [the detective Cormorn Strike's assistant] is the most entirely loveable character I've ever written. A good person but likeable - a smart woman, a kind and loyal person."

It sounds like JK Rowling has truly moved on from the Harry Potter series - which will surely create mixed feelings for dedicated fans.

"Probably the most complex plot I've ever written" - JK Rowling on her new novel as Robert Galbraith