Harry Potter creator JK Rowling has announced plans for a stage show spinoff.

The British author thrilled fans on Twitter.com by revealing she is collaborating with writer Jack Thorne and director John Tiffany to make Harry Potter and the Cursed Child, a play which will be staged in London next year.

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Rowling insists the story is not a prequel to her tale of boy wizard Harry Potter, and it is better suited to the stage than a new book.

She writes on the microblogging site, “I’m … very excited to confirm today that a new play called Harry Potter and the Cursed Child will be opening in London next year… It will tell a new story… I don’t want to say too much more, because I don’t want to spoil what I know will be a real treat for fans… However, I can say that it is not a prequel!… To answer one inevitable (and reasonable!) question – why isn’t Cursed Child a new novel? – I am confident that when audiences see the play… they will agree that it was the only proper medium for the story.”

The writer made the announcement on Friday to mark the 18th anniversary of the publication of Harry Potter and the Philosopher’s Stone, the first book in her seven-part series.