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.

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,” says David.

“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!”

David revealed 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.

“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.”

Big School returns to BBC1 on Friday, August 29, 9.30pm.