Leon is not strictly a restaurant, it's a chain of cafes and take out, but you can sit in and eat, and it does have some great gluten free and lots of other "free" options too on its healthy menu. You can find them on most high streets in central London now, dotted around Covent Garden, Kensington, Oxford Street and in the city. They do a roaring trade at lunchtime and breakfast and people love their warming healthy food. They pick and mix from around the world and have great concepts like the "Leon Lunchbox" which will range from Thai green curries to Gobi curries from India. Soups, wraps, salads and sandwiches are always available and they do a great beetroot and chocolate and orange and chocolate brownie. They also have a great range of cookbooks to buy.