We were always putting on little plays at my primary school, which I loved. Once we put on a variety show and I appeared in almost every act - it was like having my own show. But I came down to earth with a massive bump when I went to grammar school.

Wilmington Grammar School for Boys in Dartford, Kent, was quite an academic school. It didn’t have a drama department and the art block was an afterthought, housed in a derelict outbuilding.

There was no outlet for any kind of creativity, and although I staged a couple of comedy productions for assembly off my own bat the enthusiasm wasn’t there from the pupils. I felt quite lost and uninspired.

I also suffered from a growth hormone deficiency and was tiny compared with my peers. Although I wasn’t bullied, I never felt part of the gang.

When people started blagging their way into pubs, there was no way I would ever have got served, so I didn’t really have a social life outside school. I wasn’t desperately miserable, but they weren’t the happiest days of my life.

But one teacher, Simon Woolcott, restored my faith in humankind. He was very approachable and enthusiastic and obviously loved teaching. Mr Woolcott taught biology and was also my form tutor. He was quite young, in his early to mid-20s, not super-cool or trendy, just a nice, laid-back, bearded chap.

I remember one biology experiment when Mr Woolcott instructed half the class to drink two pints of water in the morning and the other half were told to drink nothing at all so that we could compare the colour of our urine during the lesson. When we went to pee in our plastic cups, I filled mine with apple juice. I remember Mr Woolcott looking slightly concerned when he saw mine, but when I swirled it around, sniffed it and then downed it in one, he roared with laughter and congratulated me on a good joke, well-executed. Any other member of staff would have slapped me in detention.

I was quite good at biology and my other passion, apart from the arts, is the natural world. I’m interested in everything to do with zoology and horticulture - I’m lucky enough to own eight acres of woodland in Essex. Obviously some of Mr Woolcott’s enthusiasm rubbed off on me. He was passionate about his subject.

He left the school before I did and went to Singapore. We didn’t keep in touch, and then about a year or so ago I went on the Jonathan Ross show. I was asked about my school and I mentioned that (Rolling Stone) Keith Richards had also gone there. We had met when I was filming Pirates of the Caribbean and we had discussed the school and he had hated it as well. So Jonathan Ross asked me if I had liked any of my teachers and I mentioned Mr Woolcott. Somebody told him and we exchanged a couple of emails, which was nice. He is back in England now, teaching in Devon.

I did A-levels in technical drawing, English and art but failed miserably. I had always been told how good I was at drawing, so I assumed that was what I would go on to do, but when I applied to art college I hadn’t been properly prepared and I didn’t have the portfolio to get in.

Towards the end of my school career I joined a local youth theatre, but it wasn’t until my late teens or early 20s that I realised I wanted to be an actor. I think I would have arrived at that conclusion earlier if the school had been more creatively inclined. But that was 20 years ago and I’m sure it’s a very different place now. And with hindsight I’m very happy I didn’t get into art college because things turned out great.

- Mackenzie Crook is appearing in ‘Jerusalem’ at London’s Apollo Theatre until 24 April. He was talking to Hilary Whitney.