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.

I think the whole attitude towards climbing Mount Everest has become rather horrifying. The people just want to get to the top. They don't give a damn for anybody else who may be in distress and it doesn't impress me at all that they leave someone lying under a rock to die.

I had never experienced anything like it before and I don't think I have experienced anything like it since [on Ruapehu]. It was my dreams coming true in a way, and from there on I tended to become more of a doer than a dreamer.

Strong motivation is the most important factor in getting you to the top

I think my strengths perhaps are that I'm determined. I may not be the best climber in the world, but I do like to sort of succeed and so that tends to drive me on, as it were, and I don't give up too easily.

June [Hillary] had been doing all these things - the Himalayas and all the rest of it - so we had done things together for a long time, and, particularly as far as our Sherpas were concerned, we had a very sound, I think, philosophy. So that made it very easy for us to agree on what should be done.

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