David Walliams has revealed he wrote a part in his comedy Big School especially for Britain's Got Talent runner-up Jack Carroll.

The teenage comedian - who often sends up his cerebral palsy as part of his act - impressed David and the other judges on the talent series in 2013 and will appear as new pupil Dean in the BBC show starring David and Catherine Tate.

David said: "Jack Carroll was perfect to play a kid in this series and he was really funny. Myself and the Dawson Brothers (co-writers Andrew and Steve Dawson) wrote the part with him in mind, and we had a lot of fun writing material for him.

"I've stayed in touch with Jack and his mum ever since Britain's Got Talent and I am delighted he wanted to be part of the series. He'll appear a little later on, but I don't want to give too much away, as he plays quite a surprising part!"

But the Little Britain star admitted his favourite character in the show is French teacher Miss Postern played by Catherine Tate, and admitted he often struggles to keep a straight face when they work together.

David said: "Catherine's performance is so perfect and so funny that I have to stop myself from laughing when she's doing it. The joy of writing for someone like that is knowing she's going to do something amazing.

"A good example was writing a scene that required her to speak Chinese. I knew when it was being written that she was going to be brilliant at it. It's a joy writing for her especially."

:: Big School returns to BBC One on Friday, August 29.