Mr Jemmett was very strict, but everybody loved him. He applied discipline only when you were naughty, not for the sake of it. We knew exactly what we could get away with.

The school was a flat-roofed, single-storey building in a residential area. It wasn’t wealthy, but we had all the things we needed. There were a couple of football pitches at the back and a garden at the front that pupils weren’t allowed into.

There were a lot of kids from big, poor Catholic families. But no matter what our backgrounds were, Mr Jemmett saw no reason why we shouldn’t become doctors, lawyers, accountants. His absolute minimum was to ensure that when a child reached 11 they had a reading age of 11, even if they had Down’s syndrome.

He was small, with a twinkle in his eye; very energetic and funny. One of the priests who came to the school was called Father Keegan, whom Mr Jemmett always pretended was Kevin Keegan’s brother. We believed him, of course, and the priest soared in our estimation.

I spoke to Mr Jemmett a few years ago, to thank him for all his help back then. He’s retired, and sounded a bit disillusioned with the way the education system has gone; he was the classic old-fashioned headteacher.

I was really good at sums from day one, and aged five I was put up a year. That meant I was only 10 when I went to Blessed Edward Jones High School, also in Rhyl. My family had moved to Denbigh, so I was travelling 12 miles each way on the bus.

The teacher who made the biggest impact was my maths master, Robert Parry. He had curly, dark-brown hair and an upright gait, and wore shoes with steel toe-caps, so you could always hear him coming. He also had this amazing giggle.

He was very strict and rigorous, as I think all maths teachers ought to be. He helped us make the most of our abilities. He took the top of the three streams in the year, and nearly everyone did O-level a year early and got grade A.

He wouldn’t let you get away with anything, and if you were out of line he would chuck a blackboard duster at you; he was one of the few teachers we respected. He used a lot of mnemonics, but wasn’t gimmicky - if you can explain things properly, like he did, you don’t need gimmicks.

I remember getting 98 per cent in one exam, and my great rival in the class, Francesca, got 100 per cent. All I’d done was make one tiny error in writing out Pythagoras’ theorem, putting “the square of the sum” instead of “the sum of the square”, or something like that. I pointed out to Mr Parry that he knew I knew the right answer. He said: “It doesn’t matter, it was wrong.” I was furious.

Mr Parry was absolutely crucial in building on my natural maths ability. When he was away for a year, I just coasted. Being in the top stream with him made a huge difference. Mixed-ability teaching is ridiculous. I can’t see the point of there being five bright pupils doing exercises, five who haven’t got a clue, and 10 who are getting all the attention.

I also think schools should have two completely separate maths courses. Most of us only need to control numbers, as opposed to mathematics, so from 13 or 14 there should be one course for those who will study mathematics and really use it, and another for those who will never need trigonometry or calculus, but who need more time to get a grounding in practical arithmetic.

At Edward Jones, I wanted to do pure and applied maths at A-level, but only four of us opted for maths and that wasn’t enough to justify Mr Parry doubling up in the timetable.

No one from the school had ever applied to Cambridge, but in 1978 I managed to get an offer to read engineering at Sidney Sussex College (I wanted to be an airline pilot and thought engineering would be a good foundation). Mr Parry was thrilled. I’m still in touch with him and I dedicated my most recent book to him. He was a genuine inspiration.

Carol Vorderman, broadcaster and author, has written eight books on maths. She has been resident statistician on Channel 4‘s Countdown quiz since it began in 1982, and also presents the factual entertainment show, Put it to the Test, on BBC1 on Tuesday afternoons