In 1950 less than 1% of British people were obese. Today that figure is 28%. We spend £3.9 billion each year on confectionery compared to £2.4 billion on fruit and vegetables. Diet-related disease is now the biggest cause of preventable illness and death in the developed world.

How did we get to this situation? According to Henry Dimbleby, every bite we take is informed by the invisible machinations of the vast, complex global food system. And on March 29 he comes to Intelligence Squared to talk about his new book Ravenous: How To Get Ourselves And Our Planet Into Shape. Few people know the food system better than Dimbleby, who is co-founder of the Leon restaurant chain and author of the National Food Strategy, and who recently quit his role as the government’s food tsar over its inaction over obesity. In conversation with Times columnist Alice Thomson, he will explain the damage our food ecosystem is doing to us and to the planet, and he will set out his strategy for creating a truly healthy and sustainable food system.