New Harry Potter star Dominic McLaughlin has revealed his reaction to Daniel Radcliffe's letter.

Last month, the Harry Potter film star revealed that he had sent a letter to the 11-year-old Scottish actor, who will be playing the boy wizard in the upcoming HBO TV adaptation of J.K. Rowling's books.

McLaughlin addressed the note during an appearance on the CBBC's Saturday Mash-Up! Live, revealing that his father handed him the letter when they were on the train home to Glasgow, Scotland.

"I got a letter from the man himself, Daniel Radcliffe. It was insane," he shared. "My Dad tapped me (on the shoulder) 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."

When asked how filming is going, he replied, "It's going amazing, it's going really well. I've made good friends with everyone, it's great to be there."

Radcliffe, who played The Boy Who Lived across eight films, revealed on Good Morning America that he wrote to McLaughlin and received a "very sweet note back".

He added that he didn't "want to be a spectre in the life of these children" but wrote him the letter 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.'"

He continued, "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 at that age.' But it's also incredibly sweet, and I hope they're having a great time."

McLaughlin plays Harry alongside Arabella Stanton as Hermione Granger and Alastair Stout as Ron Weasley. The newcomers star alongside Paapa Essiedu as Severus Snape, John Lithgow as Albus Dumbledore, and Nick Frost as Rubeus Hagrid, among others.

McLaughlin appeared on the programme to promote his new TV series, Gifted, which follows a group of Scottish teens with superpowers.