All the time I feel I must justify my existence.

We should be treating, I think, the whole issue of climate change and global warming with a far greater degree of priority than I think is happening now.

The sustainability revolution will, hopefully, be the third major social and economic turning point in human history, following the Neolithic Revolution - moving from hunter-gathering to farming - and the Industrial Revolution

Grandparenthood is a unique moment in anyone's life, as countless kind people have told me in recent months, so I am enormously proud and happy to be a grandfather for the first time and we are eagerly looking forward to seeing the baby in the near future.

To get the best results you must talk to your vegetables.

If your children want to alter society, listen to their reasons and the idealism behind them. Don't crush them with some clever remark straight away.

If you think about your and my grandchildren, this is what really worries me. I don't want them - if I'm still alive by then - to say, 'Why didn't you do something about it?', when you could have done.