So let's raise the tone of the debate. Too often at the moment we look like schoolchildren squabbling over a toy - our most precious toy, the Earth. And the danger is that as we pull in opposite directions in our global tug of war, the Earth will end up broken - or at least unable to sustain human life. That is the worst case scenario - or maybe, from the Earth's point of view, the best.

Despite what I had acchieved, I don't for a moment think I am any braver or better than anyone else. This is how I attempt to explain what gives me the stregnth to do what I do; when that thunderbolt of an idea first hit me and inspired me to row across oceans, it filled me with a sense of purpose so strong that it overcame my fears. Even when boredom, frustration, fatigue or despair threatened to overwhelm me, it was that powerful sense of purpose that kept me going.

When you stand at the bottom of the mountain and look up at the mountaintop, the path looks hard and stony, and the top is obscured by clouds. But when you reach the top and you look down, you realize that there are a thousand paths that could have brought you to that place.

My advice is don't keep asking yourself if you can do something. Just get out there and do it. You can really surprise yourself.

The Milky Way swooped diagonally across the heavens, reminding me of my utter insignificance, and at the same time my complete interconnection with everything. I was just a tiny speck of consciousness, and yet I was consciousness itself.

I'm not claiming to be anything out of the ordinary. I am not especially big or strong or brave or intrepid.

The bigger the challenge, the bigger the sense of accomplishment when you get to the end of it.