I was at school during wartime and we were governed by rules. Yet, unlike the other teachers, Mrs Dewstoe, who taught art, was uncontrolling, easygoing and had a “do as you please” attitude. I found it amazing that someone could be so tolerant and welcoming. She also got married in middle age and stayed on teaching, which was unheard of for women in those days.

She had a fantastic collection of postcards of classic paintings, which she would bring in and pin on the wall. I couldn’t get enough of these postcards - Leonardo da Vinci, Raphael, Victorian paintings, pre-Raphaelite - and that has stayed with me. Whenever I go to an exhibition, I always buy postcards and that’s in tribute to her.

I don’t ever remember her telling me why they were good or saying the pre-Raphaelites are a bit cheesy or whatever. She wasn’t judgmental. She just said that they were great works of art and left me to form my own opinion. She gave me a lifelong love of art and I became quite a good critic and consumer.

However, I was technically very bad at art and got bad marks for my own work. I was a very uptight child and I was scared of making a fool of myself so I did corny, simple, banal stuff. I remember we had to design a box and I did something very minimal. Everyone else did fantastic, ornate, thrilling designs but mine was amazingly discreet and Mrs Dewstoe said that wasn’t what she wanted.

“You’ve got to let rip,” she told me. She said I had an imagination that was precious and that I shouldn’t be repressed. It was a good lesson in life although I’ve always found letting rip hard.

Free thinking

In 1951 I went to the Festival of Britain on my own, as there was a touring art exhibition. It contained work by William Speer and Henry Moore, a lot of really rather soft-edged modern art and it got a lot of flak. Prince Philip was supposed to have said: ‘Do they know whether they’re hanging upside down or not?” which I thought was wicked and philistine.

I remember thinking, “I don’t know what to make of this,” but when I asked Mrs Dewstoe, she was wary of passing judgment. She let me make up my own mind and that was a marvellously important contribution as anything modern was frowned upon then. All my other teachers were busy saying “George Eliot, good, Daphne du Maurier, bad”.

I was a bit of a swot and was head girl but I also ran with a gang of slightly naughty girls. When I was 14 and 15 and I was quite naughty, by which I mean if the girl in front had pigtails you dipped them in the inkpot. I was also a talker and that got me into detention quite a lot. Nevertheless, I was quite competitive so I passed my exams.

I must give special mention to my English teacher. I don’t want to name her, but she wouldn’t allow me to do English in the Sixth Form as she said I wasn’t good enough. I pleaded with her, because I was passionate about writing, but she refused. I remember thinking: “I don’t need your approval to write” and it firmed up my confidence in my own willpower. I’ve since published 12 books and I have thought of dedicating one to her. Her discouragement fired me up to succeed whereas Mrs Dewstoe’s instincts were ones that I followed. They both have a lot to answer for, for different reasons.

Joan Bakewell was talking to Kate Bohdanowicz. She is co-presenting Portrait Artist of the Year, currently running on Sky Arts and On Demand