This must be the perfect place to interview an eco-campaigner: a hot house in Kew Gardens after closing time. With most visitors departed, the residents are venturing out, and an iguana shuffles calmly across our path. "This is how it should be, isn't it?" whispers Katharine Hamnett. "Eden. A perfect ecosystem. No pesticides, just all the right predators." We wander past skeins of orchids towards some Venus flytraps. "Carnivorous plants," she mutters darkly, "remind me of the fashion industry."