I think his first name was Stuart, but we weren't really allowed to know our teachers' first names. That was a no-go area.
He taught me at a fairly rough school in South London, called Ernest Bevin School, from 1977 to 1982. It was a comprehensive, all-boys school that had grown out of a grammar.
It was 60 per cent non-white, with no unifying religion. In fact, the only thing that unified the school was sport. We played everything: lacrosse, hockey, judo, karate, basketball, football, rugby. Maybe the only thing that wasn't available was snooker, and the only reason I mention that is because Jimmy White went to Ernest Bevin.
Mr Miller was a PE teacher and his influence was massive. He was a quietly confident man, with a quiet centre to him that never came across as arrogant. He was the coach for our rugby team, a team made up of boys from, mostly, West Indian and immigrant families.
None of us had any idea about rugby. We were a ragtag bunch of kids who were only on that field because we couldn't get into the football team. Mr Miller saw the size of us, saw our speed and put us into positions. He had to teach us the game from scratch. And he did - brilliantly.
That squad he was handed and trained ended up being a fantastic side. We got so much of a buzz out of not just playing the game but playing it well. We were the unlikelies: the roughnecks from South London playing the private schools, and playing them with a beautiful style of rugby drilled into us by Mr Miller.
We went to Yorkshire, beat everybody there; on tour to France, beat everybody; Holland, beat everybody there. It gave us this huge confidence, which Mr Miller inspired us to apply to our studies. We took that spirit into the classrooms.
He made us good at something that wasn't ever part of our own plans for ourselves. I credit him - and that confidence - for giving me the bravery to say out loud, and to say to my family, that I wanted to be an actor. That boils down to Mr Miller, on a cold rugby field, showing me that I could learn something from scratch - learn anything from scratch.
I only remember him raising his voice once and that kind of sums up what he was all about. He was furious when we allowed an opposing rugby team to rattle us and we behaved badly on the pitch. He wouldn't have it. He wouldn't tolerate us letting ourselves down.
Years later, I went back to the school as a grown man; I was invited back to do a prize-giving. I was in one of the school offices and, without really thinking, I swore. It slipped out. Mr Miller, without missing a beat, said, "James." And instinctively I said, "Sorry, Sir." Old habits die hard, huh?
I'm not sure I ever got the chance to tell him what an effect he had on me: in hindsight, a huge one.
Lennie James was talking to Tom Cullen
Criticalon DVD is out now and available fromBBC Shop
Born 11 October 1965, Nottingham, England
Education Ernest Bevin School, Tooting, South London; Guildhall School of Music and Drama, London
Career Actor, screenwriter and playwright whose success on UK television shows such as Cold Feet, Spooks and Critical has transferred across the pond (The Walking Dead, Jericho) and on to the big screen (Colombiana, Get On Up)