Michael Gambon responds to critics of black Hermione

For eight films she was portrayed by Emma Watson, but with Hermione's story continued on the stage, 19 years after the closing scenes of Deathly Hallows, a new actress has taken the reins.

The Cursed Child will see Hermione played by Noma Dumezweni whose casting last year saw a tidal wave of reaction from fans. Most accepted that the character's skin colour had never been specified and she could be of any race, but there was a minority who kicked back against the idea of a black actress playing JK Rowling's beloved character.

Rowling wasted no time in shutting them down.

And speaking last night at the Oxford Union, Michael Gambon, who played Albus Dumbledore for the final six Harry Potter films, also responded to critics of the decision to choose a black actor for Hermione's part.

Asked by a student for his view on the controversy surrounding Dumezweni's casting, he replied, "It doesn't matter what colour you are, does it? It doesn't make a difference if you're a black actress or a white actress.

"You'd forget it in five minutes, wouldn't you? When the tabs go up on a play, and the person who's in it starts talking, you soon forget about it. It doesn't matter what colour they are, for God's sake."

Gambon took a similar view on the suggestion that Idris Elba might play 007 after the end of Daniel Craig's tenure. "He'd be brilliant, wouldn't he? If he goes and plays James Bond, he plays James Bond. That's it, boom, stop.

"It's nonsense isn't it? It's so annoying. It's a load of bollocks."

The 75-year-old actor also discussed his decision to take over the role of the Hogwarts headmaster, following the death of actor Richard Harris in 2002.

"They rang me up and I jumped at it, I didn't have to think at all," he said of the first day on set as Dumbledore. "I turned up at the studio and did it – that’s all.

"In my first entrance as Dumbledore I had to walk up some stairs and I ran up them. The director said you can't run up them, and I said I want to run up them. And that was that."

Gambon in character as Professor Dumbledore

Gambon added that it was the author herself who informed him that his character was gay, a revelation that wasn't made public until she 'outed' Dumbledore in 2007 in front of a packed audience at New York's Carnegie Hall.

"I think they made it up as they went along," he chuckled. "She [J.K. Rowling] told me one day that Dumbledore was gay. She'd just decided that day. We'd been on for about three years!

"I started doing this on the set," he grinned, playing with his hair and fluttering his eyelashes. "The director came running over to me and asked me what I was doing.

"I said that the women who wrote this play told me I was gay. He didn't believe me, but she was there, and he went and asked her about it.

"I didn't play 'gay', I just played who I am."

"I think she's brilliant," Gambon said of his work with Rowling – which includes playing Howard Mollison in a 2015 BBC and HBO production of The Casual Vacancy – "the stuff she writes is really clever."

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But the man behind the greatest wizard of the magical world takes a surprisingly unromantic view of his role. "I didn't do Harry Potter because she wrote it. I did Harry Potter because I wanted the money," he says unsentimentally.

"And then she wrote this other play – The Casual Vacancy – and I did that because I wanted the money as well. Anything you do has something to do with how much you're getting for it."

He spoke with regret about the fact that his days on stage are over – "I just can't remember the lines any more" – but stressed that it's not made him take his job too seriously. "I've been in plays for fifty-two years and I've never stopped mucking about."

The glint in his eye as he looked out across a sea of students was remarkably familiar.