United Kingdom, Dec. 2 -- 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 f...