JK Rowling hopes Harry Potter stage play goes global

London is under Harry Potter's spell once more and J.K. Rowling hopes the rest of the world will eventually follow.

The stage play Harry Potter and the Cursed Childhad its gala opening Saturday in London's West End and is already the theatreevent of the year.

If the boy wizard's creator has her way, that will only be the beginning.

"I'd like as many Potter fans to see it as possible," Rowling said on the red carpet outside the Palace Theatre, as fans cheered and poked camera phones over crowd barriers in hopes of getting a picture.

There's already talk of a Broadway run, and Rowling said: "I'd like it to go wider than that."

Co-producer Sonia Friedman said she had big hopes for the show, which has been more than two years in the making and is slated to run in London at least until December 2017.

"Hopefully many countries at some point will get to see it," Friedman said. "But it's a big piece of theatre, it's a big endeavour. You can't just turn this around overnight."

The two-part play has been in previews at the theatrefor almost eight weeks, but few details of the plot have leaked (though those seeking spoilers online will find them).

People leaving the show are handed buttons urging them to #keepthesecrets and most have complied.

Director John Tiffany said spilling the play's secrets was "like unwrapping children's Christmas presents for them in November, in front of their eyes. And why would anyone want to do that?"

Rowling said fans have "been amazing, they've been incredible."

"It is the most extraordinary fandom, so I'm kind of not surprised, because they didn't want to spoil it for each other," she said. "But I am so happy we got here without ruining everything."

The script of the play is being published Sunday, with a global print run in the millions, so future audiences will have more opportunities to know the plot in advance if they choose.

Without entering spoiler territory, it's safe to say that the play has much to make fans rejoice. This is both an eighth instalment in the Potter saga worthy of Rowling's seven novels, and a stage spectacle to delight even the uninitiated.

The script written by Jack Thorne from a story by Rowling, Thorne and Tiffany picks up 19 years after the end of the final novel, Harry Potter and the Deathly Hallows.

Harry the orphaned boy whose destiny was to save the wizarding world is now an overworked civil servant at the Ministry of Magic, a husband and father of three. His younger son, Albus Severus, is a reluctant pupil at Hogwarts School of Witchcraft and Wizardry, struggling with the burden of his family's legacy.

• 15 things you need to know before reading Harry Potter and the Cursed Child

Fans who know the saga inside out are likely to appreciate the teeming detail of the play, which runs for five hours over two parts. It captures Rowling's richly textured magical world, with its byzantine mythology, complex history and array of fantastical creatures.

The plot is a rollicking adventure in which Albus' attempt to right a wrong goes awry. But it also has adult things to say about loss and grief, and about the complexities of friendship and family love.

The cast is anchored by the adult trio of Jamie Parker as Harry, Noma Dumezweni as Hermione Granger and Paul Thornley as Ron Weasley, and there are touching performances from Sam Clemmett as Albus and Anthony Boyle as Scorpius Malfoy, son of Harry's childhood enemy Draco Malfoy.

The actors draw both laughter and tears from audience members. But it's the work of the production crew that elicits gasps, with illusions that appear simultaneously simple and inexplicable.

Characters levitate, transform and disappear, in magic that feels hand-crafted rather than high-tech, although a great deal of technical expertise has gone into it.

Buoyed by the work of movement director Steven Hoggett and composer Imogen Heap, the show captures the warm spirit of the world Rowling has created one that has moved from page to screen to stage with its magic intact.