Sheila Dillon hears from the people attempting to revolutionise the sandwich. We're now seeing the rise of food businesses specialising in just one type of sandwich using authentic recipes from around the world. The food entrepreneurs are making everything from the Vietnamese Bahn Mi through to the Argentinean Lomito, all are sandwiches which rely on the makers finding authentic bread to match the original recipe. This development is being watched closely by the large sandwich manufacturers supplying the supermarkets. The prepared sandwich business is with £3bn a year and is based on developing new ideas. Dan Saladino follows some sandwiches through the supply chain. Sheila is also joined by the food writer Bee Wilson, the author of Sandwich: A Global History. Producer: Dan Saladino.