I consider myself very blessed educationally. After all, I went to secondary school before the 1944 Education Act came into effect. In those days, working class girls like me - even the bright ones - weren’t guaranteed a place at a good school. But I was lucky enough to gain a scholarship to Dartford Grammar School for Girls (Mick Jagger went to the boys’ equivalent).

I have no doubt my experiences there, and some of the wonderful teachers that I encountered, shaped and changed the course of my life entirely.

Perhaps the most influential of all the teachers was Miss Fryer, my headmistress. Her credo was simply that nothing empowered or liberated girls more than a good education and she obviously employed others who mirrored those beliefs. You could say she was a feminist before the term had even been invented. In my teenage years I was quite a difficult child.

I could be wild, distracted, very naughty in class. I had too much energy.

But if I was sent to Miss Fryer, she never lost her rag with me; she would always speak gently and try, through persuasion rather than coercion, to guide me. She adhered to her principals as a Quaker - a religion I took up in my middle age. She believed in fairness and listening to others and speaking only when she had something valuable to say.

It helped that I liked and respected her and felt she understood my hang-ups at that time. Throughout grammar school and, indeed, later at Rada, I had a bit of a chip on my shoulder. I felt I had the wrong accent and came from the wrong side of the tracks. But Miss Fryer showed me that knowledge and education elevates us beyond class, and she instilled a joy of learning that has stayed with me for the rest of my life.

Even now, at 73, I love learning new things and I’m endlessly curious.

She taught me that acquiring knowledge for its own sake is wonderful. I’m saddened that education these days seems to be so much more about league tables and exam results and preparing kids for a job.

It was Miss Fryer who put me both in her class and in the music lesson run by Miss Tudor-Craig. The latter was a marvellous, eccentric teacher, with cropped grey hair, sensible shoes and elastic knickers, which would show above her skirt when she sat down to play us Tchaikovsky or Bach. Her passion for classical music was contagious and I caught the bug. As a result, classical music has been a joy all my life.

It has consoled me during difficult times, particularly since John Thaw, my husband, died three years ago. Part of my “grief therapy” has been to set up the John Thaw Foundation. A charity which dedicates itself to helping disturbed children through drama seems perfect to bear John’s name. He had a difficult childhood himself. He was well on the way to going off the rails when another great teacher, John Lee, at his school, Ducie Technical High for Boys in Manchester, introduced him to Shakespeare and acting.

Throughout his life, John credited this teacher with saving him.

Both of us, then, benefited from the transforming power of great, dedicated teachers. Miss Fryer, I’m sure, has long since passed away. But her legacy lives on in the hundreds and hundreds of girls whose lives she helped to shape. We owe her so much

Sheila Hancock is an acclaimed stage and screen actress perhaps best known for her comedy roles. She also wrote The Two of Us, a memoir of her marriage to actor John Thaw. She appears in the drama After Thomas on Boxing Day, ITV1, 9pm. She was talking to Daphne Lockyer