Dominic McLaughlin was "going mad" after receiving a letter from Daniel Radcliffe.

The 11-year-old actor is taking over the role of Harry Potter from the 36-year-old for HBO's upcoming adaptation of JK Rowling's magical saga, and he was stunned to get a note from the original Boy Who Lived.

Speaking on BBC's Saturday Mash-Up! Live, he said: "I got a letter from the man himself, Daniel Radcliffe. It was insane.

"I was on the train back up to Glasgow, because we were going home, and my dad just tapped me on the train and just gave me this letter.

"I read it and then I got to the bottom, and it said, 'Dan R'. I was going mad, but I had to keep it cool. I was on the train."

Dominic was also asked about filming for the highly anticipated show, and insisted work on the series is "going amazing".

He added: "It's going really well. I've made good friends with everyone, it's great to be there."

He has been cast alongside Alistair Stout as Ron Weasley and Arabella Stanton as Hermione Granger.

Daniel recently revealed he had written to the young actor taking on his role in a passing of the torch moment.

He said on Good Morning America: "I wouldn't say that anyone who is going to play Harry has to [reach out].

"And I have a very sweet, I know a few people who are working on the production so I wrote to Dominic and I sent him a letter and he sent me a very sweet note back."

The Woman in Black star noted he didn't want "to be a spectre in the light of these children", referring to Dominic, Alastair and Arabella, but was keen to wish his successor well.

He added: "I just wanted to write to him to say, 'I hope you have the best time, and an even better time than I did -- I had a great time, but I hope you have an even better time.' And I do."

Daniel, who was also 11 when he filmed the first Harry Potter movie, can't help but feel an urge to protect the new young stars.

He said: "I just see these pictures of him and the other kids and I just want to hug them.

"They just seem so young. I just look at them and say, 'Oh it's crazy I was doing that.' But it's also incredibly sweet and I hope they're having a great time."