I certainly wouldn’t describe myself as a model student. At Harrow, my main interests were drink, girls, smoking and pissing off anyone in authority. By the time I reached the sixth-form, my days were numbered.

I was asked to leave before sitting my A-levels. I don’t remember the exact offence, although I think it was something to do with a fight and some indiscretion with a girl at the sixth-form ball. In a nutshell, I probably behaved like an idiot because I wanted to leave. At the age of 18, I just couldn’t stand the constraints of Harrow and being told what I could and couldn’t do. So I forced the issue myself.

I’m sure I would have done so much sooner if it hadn’t been for Martin Tyrell, my English and theatre studies teacher. He was an amazing man and though I never enjoyed Harrow, he alone seemed to make the experience worth it.

He was passionate, committed and inspirational. He wasn’t one of those clock-watching teachers, either. I can remember many late evenings when he would go over and over plays that we were studying, bringing them to life, fuelling us with the passion that he had for the work himself. He had a way of energising his students, bringing out the best in them. I never once detected a moment of apathy or boredom in him.

He could, of course, have been an actor himself. He certainly had the talent. When you watched him, he could be sinister, menacing, but he could convey such a tremendous range of emotion.

He might well be the best actor I have known, but teaching was his calling, something he loved. He liked to share the love around, too, and he didn’t have favourites. Although he nurtured many talents, including actors such as Benedict Cumberbatch and James Dreyfus as well as me, he was equally generous to anyone who expressed an interest in the subject he taught. Everyone was welcome in his class. If you asked for his help, he was always there to give advice and guidance.

I credit him, more than anyone - including my own father, James Fox - for putting me on the road. I learnt more from him about acting, too, than I did even from my time at RADA. Indeed, when I was applying for a place there, I returned to Harrow and asked for his help. He took me into the theatre and we went through the pieces I was going to perform. He did them himself and, basically, all I really needed to do was to copy them myself. As I said, he was a brilliant actor.

I suppose one of the things I loved about him was a sense that he was perhaps a kindred rebel. Unlike all the other stuffy teachers in their braces and robes and mirror-shiny shoes, he was much more of a tatty, linen-jacket sort of person. He also smoked, while in the confines of the school - shocking and unheard of. I always thought of him as a bit of a Harrow hippy.

Clearly, though, he was much more at home in the place than I was and he has an enduring loyalty to the school at which he still teaches. He has got quite cross with me in the past for saying mean things about the place in interviews. So I try to rein it in a bit these days.

He has, hopefully, forgiven me because whenever I’m in the theatre I invite him and he comes along. I saw him at Christmas, when he came to see me in Lara and Zhivago, a play my father was directing at Pushkin House in London.

I wouldn’t say that we are mates. There is something still quite formal and teacher-pupil about our relationship. But I do hope that he knows how much affection and respect I have for him. It might please him to know that the more distance I have from my school days, and the more I encounter people from different walks of life, the more I can see the privileges of having been to Harrow.

Going to an all-boys public school was not my cup of tea and not what I would choose for my own son, Winston. But at the same time, it certainly had its good points, too. And the very best of these, of course, was Martin Tyrell himself. Laurence Fox was talking to Daphne Lockyer.