She was quite young - in her twenties and didn’t look authoritarian, but she had no problems with discipline because she had an aura around her that inspired respect. I had a great relationship with her, but she did not try to be friends or court being liked. In fact, she was rather abrasive, but also dry and funny. Yet she was the only teacher I ever went to with a boyfriend problem, although she would not have been most people’s first choice for a friendly chat.

I still remember the books I did with her for A-level English literature - Tender is the Night, Decline and Fall . She gave me a sharp appreciation of what’s good in writing and what makes a book good.

I found her very inspirational and she allowed me a certain amount of leeway.

She let me sit through her A-level English literature lessons drawing, as long as I was listening and contributing. English was easily my best subject, but she wasn’t about to tell me how brilliant I was. She pushed me to do better, which is what I needed. She was committed to the state system and didn’t allow standards to slip.

She left the school shortly after I did.

When I went to say goodbye to her I remember callng her Lucy - it had definitely been Miss Shepherd until then.

She gave her all to the job, and teaching teenagers is probably something you can only do for so long. She’s now advising adults on career choices, and I should think she’s very good at it.

I heard from her again after Harry Potter and the Philosopher’s Stone was published. It was one of the best letters I’ve received. Professor McConagle (the strict-but-fair teacher in the Harry Potter books) is based on her.

Pearl Biddle is bound to appear in one of my books at some point, if only because of her wonderful name. She tutored me at home for French A-level when I was 17 (I read French and classics at university).

She was a cultured, widely-read woman married to a farmer and with two young children - and was quite young herself.

When we had finished the French, we used to sit and talk about everything else, mainly books. I so looked forward to seeing her. She was the key person who taught me that “intellectual’ is not a dirty word and that there was no need to apologise for wanting to read.

At that stage I didn’t have anyone else to talk to about books. It wasn’t the coolest thing to be too bright at my school. I was a bit of a Hermione (Harry Potter’s studious friend) and had suffered for it.

I also wore glasses and I was determined that in Harry Potter, the trainee wizard, I would create a hero who wore glasses - I was so tired of books in which the brainy kid wore glasses. Pearl made it possible for me to be brainy - she wanted me to do as well as I could.

Reading and writing have been my passion since I was tiny. but I didn’t show my writing to teachers, or anyone. I kept Harry Potter to myself for seven years before the first book was published. By then I had the outlines of seven books- one for each year that Harry spends at wizards’ school. It’s as if we’ve both had rite of passage.

* Joanne Rowling’s Harry Potter novels for children are published by Bloomsbury.

‘Harry Potter and The Philosopher’s Stone’ won the Smarties Prize last year and is on the shortlist for the Carnegie Medal, which will be awarded on July 15. The second novel, ‘Harry Potter and the Chamber of Secrets ’, is published this month.

Joanne Rowling was talking to Geraldine Brennan.