Alex Haw of architecture firm Atmos teaches "urban agriculture" at the Royal College of Art, where he is something of a guru to art students drawn to the idea of urban growing as a means of self-expression. "I think there is a massive simmering interest in food awareness, food stability and food crisis," he says. "Are we going to be able to feed ourselves? Perhaps gardening is also a bridge between the privacy of capitalism and the idea of collectivism. It's a gift culture, because you garden for yourself and for others as well. It's a way of transmuting our inbuilt materialism - our possessions - into something more sociable."