Feature: Magic and controversy as Harry Potter hits the West End stage

With just 24 hours before the curtain rises on the first ever stage production of a Harry Potter story, creator JK Rowling has reacted angrily to a storm blown up on social media.

Audiences at the first preview Tuesday at the Palace Theatre in London's West End will be the first to see Potter's fellow wizard Hermione Granger played by a black actress.

In the eight Harry Potter films, screened to packed movie theaters across the world, the part was always played by British white actress Emma Watson.

In the eagerly awaited new play, Harry Potter and the Cursed Child, the part is played by award-winning black actress Noma Dumezweni, winner of one of Britain's top theater awards, the Olivier.

The casting of a black actress to play Hermione Granger has sparked a frenzy on social media sites, with people divided on whether the role should have followed the films and gone to a white actress.

Rowling has joined the frenzied outpouring of views, defending the decision to cast Dumezweni in the play.

The stage production has broken all West End records by selling 175,000 tickets in just 24 hours, and is already being hailed as the theatrical event of the year.

Rowling branded critics of the decision as a "bunch of racists", telling the Observer newspaper: "With my experience of social media, I thought that idiots were going to idiot (sic). But what can you say? That's the way the world is. Noma was chosen because she was the best actress for the job."

The author added: "I had a bunch of racists telling me that because Hermione 'turned white' -- that is, lost colour from her face after a shock -- that she must be a white woman, which I have a great deal of difficulty with. But I decided not to get too agitated about it and simply state quite firmly that Hermione can be a black woman with my absolute blessing and enthusiasm."

Rowling insists there is no reason why Hermione should be white as her books don't explicitly mention her race or skin colour, and she is often portrayed as black in fan art.

Director John Tiffany, who cast Dumezweni, said he was surprised by the opinions expressed on social media.

Tiffany said: "What shocked me was the way people couldn't visualise a non-white person as the hero of a story. It's therefore brilliant that this has happened."

After its previews, the two-part production opens at the Palace Theatre in London's West End at the end of July. Audiences for previews have been asked to arrive an hour early so they can have their bags searched before entering the auditorium.

Secrecy surrounds the storyline but it is expected to pick up where the final book left off. Harry Potter is now an overworked employee of the Ministry of Magic, married with three school-age children.

The play focuses on Harry's youngest son, Albus, who "must struggle with the weight of a family legacy he never wanted".

Rowling has contributed to the play, but has not written the script, though in her Observer interview she said Harry Potter had never left her.

"Just because I've stopped on the page doesn't mean my imagination stopped. It's like running a very long race. You can't just stop dead at the finishing line. I had some material and some ideas and themes," adding that she, Tiffany and playwright Jack Thorne had "made a story". It has taken the trio two years to complete their project. Endit