As 'Harry Potter and the Cursed Child' opens for previews at London's Palace Theatre, Jk Rowling once again addresses the onslaught of racially-charged criticism she has endured for giving her blessing for a black actress to portray an older Hermione in the play, despite the fact that she was white in the movies.

JK RowlingJK Rowling tackles the racists once again

Such a progressive move was always going to be controversial; Rowling tried to counter the attacks after it was announced that Olivier award winner Noma Dumezweni would be playing Hermione Granger-Weasley by simply reminding fans that her colour was never defined in the novels. 'Canon: brown eyes, frizzy hair and very clever. White skin was never specified. Rowling loves black Hermione', she wrote on Twitter. However, now she's addressing the slew of arguments she's received since making the comment.

'With my experience of social media, I thought that idiots were going to idiot', she told the Observer in an interview. 'But what can you say? That's the way the world is. Noma was chosen because she was the best actress for the job.

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'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.'

If these minor distinctions bothered some so-called Harry Potter 'fans', they barely registered with others; Hermione is very often portrayed as a black girl in internet fan art, after all, even if for many Emma Watson is the face of the witch. Dumezweni was chosen for the role by director John Tiffany, who couldn't believe the backlash that came after the announcement. 'What shocked me was the way people couldn't visualise a non-white person as the hero of a story', he said. 'It's therefore brilliant that this has happened.'

'Harry Potter and the Cursed Child' will open to the public in its two parts at the end of July.