Harry Potter author JK Rowling has expressed her delight that Harry Potter And The Cursed Child would premiere without any spoilers leaking.
Arriving at the Palace Theatre in London on Saturday, she praised fans who managed to keep the story a secret: "They've been amazing, they've been incredible, and you know what it is?
"It is the most extraordinary fandom so I'm kind of not surprised they didn't want to spoil it for each other but I'm so happy we got here without ruining it."
The play opens on Saturday after eight weeks of previews, but Rowling has set her hopes on the play travelling around the world.
When asked on whether the show would go to Broadway, New York, she said: "I'd love it to go wider than that. I'd like as many Potter fans to see it as possible."
London Mayor Sadiq Khan spoke of his pride that the play was launching in the capital.
He said: "Many thanks to JK Rowling for ensuring the premiere is here. What's important is that the world premiere is here in London, and we should be really proud."
The Cursed Child opening in London will immediately be followed by the midnight release of the play's script book, allowing fans across the globe to find out what happens to the boy wizard and his friends.
Set 19 years after events of the seventh and final book, The Cursed Child brings back Harry Potter, now grown up and an employee at the Ministry of Magic.