There were some guerrilla gardeners already in existence before I launched the blog, but their initiatives weren't very organised. The site connected people. I just collect info and give ideas, like "seed bombing" — planting things in hard-to-reach places. Today there are 9,000 people across the world registered on the site.

The movement can sometimes get political. Last Monday around 60 of us went to Heathrow airport for a day of gardening. It was our way of saying no to the expansion of the airport. Along with Greenpeace activists, we planted flowers from the Chelsea Flower Show in front of the airport.

Most of the time the police ignore us. It has happened that they've fined us or stopped us from filming our work. I have lost two gardens of the various ones I've created, one to a road reconfiguration and the other to a new tower block. But the police haven't destroyed any of my work. That's because I focus guerrilla gardening on neglected public land, so there's seldom a compelling reason for the landowner to bother removing it.