Tristan Jones-Perry was my maths teacher at Westminster public school.

“TJP” we called him. I wasn’t a talented mathematician, but under him I did really well. He was an amazing teacher for two reasons.

First, he was a tremendously frightening person, which meant he commanded your total attention in class. You didn’t dare to daydream, because you knew he would notice. He would call on you and you wouldn’t be able to answer and he’d unleash hell. I don’t mean physically; he just had a very frightening way of shouting.

Second, he was a great communicator. He was very good at getting across ideas and talking you through problems. Everyone in his class got an A at O-level. He was that good.

TJP was tall and losing his hair. He had an imposing physical presence because of his height and his face. He had an intensity about his eyes, and when he got cross - it often seemed that he was about to lose control, but he never quite crossed the line - a vein in his forehead would start to throb and he would say, “What the hell do you think you’re doing, boy?”

People did impressions of him because he had a distinctive way of speaking.

He would punctuate his statements with an interrogative “hmm?”. I’ve always thought the “hmm?” was important because so much of good teaching is about throwing in those interrogatives so that the pupils know the teacher is involved. He wasn’t talking at you, he was explaining something; it was like saying, “Are you following this?”

He’d pick you at random and say, “So what do we do here?” and you lived in fear that he would call on you and you would say, “I’m sorry but I really don’t know what you’re talking about”. Then he would say, “I thought you’d be paying attention boy”.

He gave you a lot of homework, but you did it because you didn’t want him to shout at you. If he wanted to punish you he’d say, “Come and see me at 7.00 tomorrow morning”. (I was boarding). It only happened to me once. I think he caught me copying someone else’s homework. He didn’t shout at me, he just gave me a talking to. He said, “Don’t become vague”. That was his expression. It was like saying, “Don’t be wishy washy; you know what you have to do, so just do it”.

If you made mistakes with your homework, he would come over to your desk to discuss it with you. He was a heavy smoker, so there was a strong smell of cigarettes; I don’t know if that helped focus us or not. But he would explain, take you through all the things you got wrong. He’d never just mark something wrong and leave it at that; he would explain why you got it wrong.

He was also very egalitarian, and didn’t have favourites. I had no sense that he was especially interested in me. He seemed to be interested in everyone.

Until I got my A in O-level maths, I had never thought of myself as being particularly good at the subject. Partly as a result of that result, I went on to do maths A-level, but TJP wasn’t my teacher and I stopped paying attention. I’d just draw cartoons in class and coasted on what I’d learnt doing the AO-level. I managed to get a B, but if TJP had been my teacher I’m sure I would have got an A.

He later became the headmaster of Westminster, and retired last July. He was a pupil at the school as well, so his association was a long one, but I remember someone telling me he had a reputation that went beyond the school for being a very effective teacher. Someone once said he was famous for being the best teacher in Britain, but I don’t know if that’s really true.

I don’t know how they could even rank that.

Broadcaster and writer Louis Theroux was talking to Sheryl Simms

Portrait by Russell Sach

The story so far

1970 Born Singapore

1974-78 Rathfern primary, Lewisham, and Allfarthing primary, Wandsworth, London

1978-83 Tower House prep, East Sheen

1983-87 Westminster school

1988-91 Studies modern history at Magdelene College, Oxford

1992 Writer and reporter for alternative magazine in San Jose, California

1993 Works on Spy Magazine in New York

1994-95 Correspondent on Michael Moore’s TV Nation

1996-2002 Writes and presents Weird Weekends and When Louis Met... on BBC.

Both series win Baftas

2005 First book, The Call Of The Weird: Travels In American Subcultures, published (Macmillan, pound;17.99)