Comic turned Britain’s Got Talent judge David Walliams educates us on his new sitcom, Big School (BBC1, Friday), set at a secondary school…

This is the first sitcom you’ve written, can you tell us about it?
“I play chemistry teacher Mr Church who’s never married and lives alone. In the first episode, Catherine Tate’s character, Miss Postern arrives as the new French teacher – unbelievably she’s never been to France – and Mr Church falls hopelessly in love with her. But he has a rival in Mr Gunn, the PE teacher, who thinks he’s god’s gift to women and is played by Phillip Glenister. This pair compete over who’s going to take her out on a date.”

So is there a will-they, won’t-they love story going on?
“If he was a confident person and they got together on Day One there’d be no comedy. I had to keep that ball in the air for as long as I could. I’m quite socially inept, a bit like Mr Church, so I like dysfunctional characters. Catherine Tate is amazing – I’ve always really wanted to work with her.”

Who play the other teachers?
“We’ve got a great cast. As well as Catherine and Phillip, there’s Frances De La Tour as the headmistress and Joanna Scanlan (The Thick Of It’s Terri) as an interfering drama teacher. There’s also a marvellous music teacher played by Daniel Rigby. He thinks he’s really cool and wants to be in a band.”

So what were you like at school?
“School is a great place to learn how to be a comic because you learn how to poke fun at authority. I wasn’t badly behaved, just attention-seeking. Getting laughs in front of teachers, as well as doing school plays was what made me know I wanted to get into comedy.”

Have you considered asking your Britain’s Got Talent boss, Simon Cowell to come in for a cameo?
“There is actually an episode where the school puts on a version of a ‘…Got Talent’ show and I did think it would be fantastic if he came on stage at the end of the scene. Although, I don’t think it would fit – it would probably shatter the reality of the piece!”