I had two inspirational teachers at my preparatory school and it is impossible to separate them. Nichol Marston and Gerald Barber were joint headmasters of Ludgrove School in Wokingham, south-east England, and they were a dynamic pair.
They taught me between 1982 and 1987, when I was aged 8 to 13, and were a classic "good cop, bad cop" duo. Mr Marston - short, stocky and a firm believer in tweeds - was a strict but inspirational figure. He always believed we were better, cleverer and more capable than we ever felt. He was like a ball of fire, constantly patrolling and cajoling.
Mr Barber, by contrast, was softer, more family-focused and great fun. He was tall, slim, good-looking - like a modern-day David Niven - and he always had a hearty laugh.
Their special qualities were summed up for me one day when I was 10. We had a maths test that Mr Marston had set us. I remember getting no marks at all. He drew a zero in a circle and said to me that "fried eggs" like this would not help me to change the world. Then he stormed out, furious.
Later that day, Mr Barber came up to me and told me not to worry too much about my poor performance in the maths test. Instead, he suggested, I should focus on trying to hit a six in the school cricket match later that afternoon - and also on looking out for a younger student who was feeling homesick. I doubt I managed to hit that six but Mr Barber's words were really about building character and good attitudes.
The two men's teaching styles had much in common: they wanted to encourage and challenge, and they always kept the focus on effort and kindness, both of which they believed mattered more than excellence or prowess.
Mr Marston did sometimes get pretty angry with us if he felt we weren't trying our best. He would stamp his right foot and scratch his head frantically, while muttering, "Ay, ay, ay, come on fellow." That was when you knew you were in real trouble.
Both teachers have had a powerful influence on my outlook and the way I try to conduct myself. They inspired me to go for it in life and I am sure they helped to hone my drive to become an adventurer and explorer. My exploits - such as climbing Mount Everest, paramotoring over the Himalayas and travelling along 2,500 miles of the Northwest Passage, a sea route through the Arctic Ocean, in a small, rigid inflatable boat - all had humble beginnings.
They also taught me that real wealth is found in the quality of our relationships and not in bank balances or any status symbol. I have always tried to remember that in my dealings. They ingrained in me the value of hard work, faith, family and good friends as the cornerstones of a fulfilling life.
We stayed in touch after I left school and today the connections continue, as my 10-year-old son Jesse attends Ludgrove, which is now run by Gerald Barber's son Simon. Nichol Marston still lives in the grounds with his dog, Bunker.
Sometimes we don't get to express our thanks - and despite giving me many "fried eggs" at school, these teachers were the inspiration that encouraged me to fulfil my potential. For that I want to say a really heartfelt thank you.
The last episode of Bear Grylls: Escape from Hell will be shown on the Discovery Channel on Monday at 9pm, and Bear's Wild Weekend with Stephen Fry will air on Channel 4 in December.
Life in the wild
Born: 7 June 1974, London
Education: Ludgrove School, Wokingham, Berkshire; Eton College, Berkshire; Birkbeck, University of London
Career: Adventurer, author, television presenter.