I was a late developer. I struggled to concentrate at primary school and my parents thought I would end up sinking to below average, so they figured I would do better going where the average was higher. They sent me to one entrance exam where I walked around the classroom, but eventually I got into Kingston Grammar School in Surrey.

We lived in Woking and it was quite a way away, so it was bus-train-bus, a lot for a 10-year-old. I was the only one from my primary school who went there, but at least it was a mixed school so it wasn’t too much of a leap.

It was a good school, not too big, about 600 pupils, the atmosphere was great and I enjoyed the opportunities I had to play sport. Looking back, I realise there was quite a difference in the standard of teaching. I needed to be inspired to learn and if teachers didn’t show enthusiasm, I didn’t pick up on it and tended to just drift along.

I always liked biology, chemistry, geography, history and I really struggled with physics and maths. I failed physics in Year 10 but I got an A at GCSE, and that was down to Dr Pumphrey.

Physics is something that people either grasp quickly or they don’t get, and it is quite easy for a teacher to move on to another section without everybody understanding, especially if people aren’t prepared to put their hands up. Once you grasp it, it is something you can really work with. Dr Pumphrey took care to make sure we all understood it, as well as making sure the clever ones weren’t doing nothing.

I only had him for a year, but he made a massive impact on me. You could tell he wasn’t just going through the motions and he cared whether you understood it or not. Part of it was because he wanted us to pass, but he put a lot of thought into how he planned his lessons and how he could make us understand it.

He used a lot of demonstrations and practicals and he was always quite good at setting homework. We had textbooks with the answers at the back, but he would set work that wasn’t in the book, which made you think about it more, and if you think about it you have to understand it.

He wasn’t strict, but he wasn’t soft either, and there was a bit more respect because he was a Dr rather than a Mr. He didn’t seem to need to call on discipline, although it wasn’t a badly behaved school. It is when people don’t understand that they get bored and play up.

He made a massive difference, without a doubt. I remember saying that to him afterwards - to go from not really understanding physics to passing it well was a big thing. A few years ago I put him down as an influential teacher in an article and he sent me a letter saying it meant a lot. It’s good to know it makes a difference.

Teachers have a huge influence. I did a PGCE and taught geography for two years. I didn’t know what I wanted to do and I thought it would be a good skill to have. I didn’t particularly enjoy standing up in school giving a talk so I thought I would benefit from learning how to do it. I had a good grasp of geography, but I don’t think I spent enough time learning how to get it across.

I think that the whole teaching system should be more vocational. I don’t see the relevance of more and more knowledge: it’s much more important to get people to understand.

James Cracknell won gold in the coxless fours in the 2000 and 2004 Olympics and is now a sports presenter and journalist. He is consultant editor for ‘Body Science’, published by Dorling Kindersley on June 1. He was talking to Nick Morrison.