When we were walking through the narrow alleys [of the Mathare Valley slums], it was literally impossible not to step in the raw sewage and the garbage alongside the little homes. But at the same time it was also impossible not to see the human vitality, the aspiration and the ambition of the people who live there.

For too much of history, we've viewed the world's precious resources - both environmental and human - as things to extract, to make the most of in order to maximize their potential.

I believe the government should ensure all children are provided with a good education.

I have also been touched by the dark side of power and leadership.

Failure can be an incredibly motivating force.

Girls and women are most victimised in societies where boys and men are disempowered.

There are cases where government-to-government aid actually has worked. Look at the eradication of smallpox and the near eradication of polio. But these are really top down solutions that require government-to-government support and aid.