Good planning is important. I've also regarded a sense of humor as one of the most important things on a big expedition. When you're in a difficult or dangerous situation, or when you're depressed about the chances of success, someone who can make you laugh eases the tension.

I can remember when I first went into the Himalayan area way back in 1951. Money, for instance, was not important at all to the local people. But now, finance has become just as important to them as it is to us, and this is a change maybe not for the better.

Nobody climbs mountains for scientific reasons. Science is used to raise money for the expeditions, but you really climb for the hell of it.

I think I mainly climb mountains because I get a great deal of enjoyment out of it. I never attempt to analyze these things too thoroughly, but I think that all mountaineers do get a great deal of satisfaction out of overcoming some challenge which they think is very difficult for them, or which perhaps may be a little dangerous.

While on top of Everest, I looked across the valley towards the great peak Makalu and mentally worked out a route about how it could be climbed. It showed me that even though I was standing on top of the world, it wasn't the end of everything. I was still looking beyond to other interesting challenges.

When I was climbing, I built up a close relationship with the Sherpa people.

My relationship with the mountains actually started when I was 16. Every year, a group used to be taken from Auckland Grammar down to the Tangariro National Park for a skiing holiday.

I have enjoyed great satisfaction from my climb of Everest and my trips to the poles. But there's no doubt that my most worthwhile things have been the building of schools and medical clinics.

My most important projects have been the building and maintaining of schools and medical clinics for my dear friends in the Himalaya and helping restore their beautiful monasteries, too.

I think it all comes down to motivation. If you really want to do something, you will work hard for it.