My early education was varied, alternating between state and private schools. The first was Sherrards Wood, a private school in Welwyn Garden City, Hertfordshire, where I stayed until I was six when I think my parents ran out of money. I was sent then to the local state primary school, Parkway, run by a lady who is memorable, but for the wrong reasons. Miss Coe beat children. She also forced me as a left-hander to write with my right, so I was sent back to Sherrards Wood.

I had a wonderful time there but I didn’t learn anything that was appropriate for passing the 11-plus, so my parents put me back into the state primary, which by this time had a different head. I was always an ambitious child, and the teaching must have been very good because out of the 30 children in that class 28 went to university. Eleven went to Oxford or Cambridge - two of them became professors.

I went to Hitchin Girls’ Grammar, which I chose because it was a beautiful building in a beautiful environment, but I hated the uniform.

I was always interested in painting and drawing, and my best teacher, with whom I kept up long after I left school, was Miss Janet Mothersill who taught art. She was the first person to say to me: “I think you can do it, you have potential.” She motivated us because her judgments were considered. From her I learned the most important lesson you need to know as a teacher, and that is how to give a young person hope that they can be good at something.

It was my interest in art that led me to a fascination for natural history. During the holidays I went to a field study centre to take a course on botanical illustration. Jim Bingley was the warden, and he introduced me to the world of the pond and the miscroscope.

The next teacher of note was Dr Eileen Oldfield. By this time I was 35, had been to Somerville, Oxford, and London to read zoology, done illustration and exhibition work, gone into publishing, married and had three children.

I was anxious to get my youngest child, Tom, into a particularly good nursery school which was full and was told that the only way was by being a priority case. This meant having a parent who was a doctor, a nurse or a teacher. I decided to train as a teacher - this was in the Seventies when there was a dire shortage - and went to the Maria Gray College in Twickenham. There I was interviewed by Dr Oldfield. Even though we later became friends, I never confessed the real reason why I became a teacher. Tom died when he was 17, but if it wasn’t for him I should never have had my third career.

Eileen Oldfield, like Miss Mothersill, was inspirational. From the beginning she talked about my becoming a head of department. I found her easy to talk to and, like Miss Mothersill, she was extremely well organised. She taught me how to prepare lessons and expected visual aids for each one. I gave the sort of lessons I would have loved when I was a child.

I have tried to emulate both Miss Mothersill and Dr Oldfield, to listen to young people, to treat them the same and give them hope. Both these women believed in me, and I responded to that.

Dame Tamsyn Imison has been headteacher of Hampstead School, London, since 1984.She was talking to Pamela Coleman