Jk Rowling has sent out a plea to fans to keep the plot of play Harry Potter and the Cursed Child a secret. Previews of the production begin tonight at the Palace Theatre in London’s West End, before it officially opens on June 30th.

On Twitter Rowling shared a video which she captioned: ‘Potter fans have always had each other’s backs. Today I’m asking you to #KeepTheSecrets of #CursedChild’. “You’ve been amazing for years at keeping Harry Potter secrets so you didn’t spoil the books for readers who came after you,” Rowling said in the video message.

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“So I’m asking you one more time to keep the secrets and let audiences enjoy Cursed Child with all the surprises that we’ve got to the story.” Newspaper theatre critics have also been asked to wait eight weeks before publishing any reviews.

Tickets for the show have already sold out until 2017 and are now selling for up to £800 on secondary ticket sites. Fans who weren't lucky enough to snatch a ticket will now have to pay massive prices or wait until May 2017.

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While Rowling has been careful not to give too much about the play’s plot, she has promised fans it will be ‘‘unlike anything people have seen before’. “I think that, as a theatrical experience, as a play, it will be unlike anything people have seen before,” Rowling told The Observer. “And once people have had this theatrical experience, they will understand why this was the perfect medium for the story.”