J.K. Rowling has defended the casting of a black actress as Hermione Granger in 'Harry Potter and the Cursed Child'.

JK Rowling

JK Rowling

The author insists she "never specified" the ethnicity of the popular witch when writing her series of books, so can't understand why some people are outraged that Noma Domezweni will take on the role in the spin-off play.

She tweeted: "Canon: brown eyes, frizzy hair and very clever. White skin was never specified. Rowling loves black Hermione (sic)"

And while Paul Thornley doesn't have Ron Weasley's trademark red hair, fans have been reassured that he is "ginger in his soul".

Playwright Jack Thorne posted on Twitter: "Noma, Jamie & Paul will be the most brilliant three. We're very lucky to have them. And to assure all doubters - Paul is ginger in his soul."

Joining Paul and Noma in the play will be Jamie Parker as the titular now-adult wizard and J.K. is delighted with the casting of all three lead actors.

She said: "I'm so excited with the choice of casting for Harry Potter and the Cursed Child. I can't wait to see Jamie, Noma and Paul bring the adult Harry, Hermione and Ron to life on stage next summer."

The two-part play is due to make its debut at the Palace Theatre in the heart of London in summer 2016.

In the movies Harry, Hermione and Ron were played by Daniel Radcliffe, Emma Watson and Rupert Grint.