Dairy-free diets are now in vogue. Soya yoghurts, almond milk, coconut ice cream, and tofu are widely sold in supermarkets. Vegan caf s and restaurants are popping up everywhere. And there's plenty going on in the media too: as celebrities ditch the white stuff, scientists debate the impact of veganism on climate change. It wasn't always like this. Back in the 1970s and 1980s, eating a plant-only diet was seen as a far more radical and counter-culture...