Rob Brydon has credited his comprehensive school drama teacher with giving him the self belief to become an actor.
The Gavin and Stacey star is appearing on the London stage in Future Conditional at The Old Vic, playing a teacher in Tamsin Oglesby's thought-provoking play about the issues surrounding education in the UK today.
Brydon, 50, said: " The bottom line is, whether it's private, state, faith, academy, it's the teacher.
"You can be in what's thought of as a fantastic school and if you don't get a good teacher, then you're sort of scuppered."
He added: "My drama teacher at Porthcawl Comprehensive School, Roger Burnell, who is still now a very prominent force in Wales in drama for young people, he and I are still very good friends.
"He was the one who gave me the confidence, he was the one who gave me the self-belief that I could go on and make a career of this. He was very important to me.
"He gave me self-belief and good practical advice. There was nothing airy-fairy about his drama classes, it was how he related to the children. Above and beyond his skills as a director was his way with young people.
"Once I found him in the fourth form at school I spent all my time in the drama studio, that's where I wanted to be.
"I went to drama school afterwards because I wanted it to be like what I loved at school all day long."
Fellow Gavin and Stacey star Ruth Jones, who co-wrote the series with James Corden, also went to Porthcawl Comprehensive and was taught drama by Mr Burnell.
Future Conditional opened last night to an audience that included Ed Miliband, Tamsin Greig and Bill Nighy.
The comedy focuses on many aspects of education, from pushy parents trying to get their children into the right school, to government focus groups and the university admissions process.
Brydon plays secondary-school English teacher Crane and appears on stage alone, addressing an imaginary class.
The Welsh actor admitted: "I'm playing to an empty stage where I'm imagining the schoolchildren at their desks, and the audience, we hope, imagine them too.
"That's been hard, that is challenging. You have to have a very solid mental image of what you're looking at."
Brydon hopes the play will provoke debate about the state of education.
He said: "I think the play is remarkably zeitgeist-y in terms of the questions about education, but also about immigration as well.
"In that sense it couldn't be more timely. It's very much a thought piece, state-of-the-nation, talking piece. You come out of it and you're going to want to discuss it."