How does Sir David Attenborough do it? At 95 he is still as active as some 60 year olds. He is still drawing huge audiences with his latest BBC series, The Green Planet. On a shoot he is still prepared to travel, get up early and work through the day. Is his energy genetic? Or does it perhaps stem from a combination of focus, his undiminished passion for nature and the fact that he is still doing something with a purpose? (Accompanying image courtesy via Wikimedia Creative Commons)