Harry Potter still casting a spell on opening night of The Cursed Child drama

Harry Potter fans will be hoping to catch a glimpse of stars such as JK Rowling at the opening gala of Harry Potter And The Cursed Child.

"Pottermania" will reach fever pitch as the Cursed Child opening in London is immediately followed by the midnight release of the play's script book, allowing fans across the globe to find out what happens next to the boy wizard and his friends.

As the play officially opens at the Palace Theatre after nearly eight weeks of previews, audience members will expect a magical experience after rave reviews from critics.

Set 19 years after the 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.

Harry and his wife Ginny Weasley wave off their youngest son Albus Severus to their old wizarding school, Hogwarts - but once there, Albus struggles with the weight of his family legacy and goes to extreme and dangerous lengths to right the wrongs of the past.

Daily Telegraph critic Dominic Cavendish said that "British theatre hasn't known anything like it for decades".

He raved: "It's a triumph. Not an unqualified one - there are some quibbles - but in all key respects, it grips, it stirs, it delights."

The Independent's Jack Shepherd awarded the play five stars, writing: "It's quite apparent this isn't written to be either a book or a tie-in film; it's a spectacle for the theatre, one that is filled to the brim with fan service and magical imagery that will amaze."

The two-part play stretches over five hours and was co-devised by Rowling, written by Jack Thorne and directed by John Tiffany.

Jamie Parker plays Harry, who is joined on stage by his school friends Ron Weasley (Paul Thornley) and Hermione Granger (Noma Dumezweni).

Albus actor Sam Clemmett has been a big hit, as has Anthony Boyle as Draco Malfoy's son Scorpius.

Despite the script's release and the play's opening, audiences will still be urged to "keep the secret" as they leave.

Rowling herself has asked fans not to reveal any plot details after seeing the show.

The Cursed Child is currently sold out, but another 250,000 tickets are set to go on sale next week as the play's run has been extended until December 2017.