In 1980, Marks and Spencer trialed cold sandwiches at five stores. Staff didn’t think that shoppers would buy such a homely meal but before long 105 stores were selling it. Then every supermarket and store started selling cold sandwiches turning them into Britain’s most popular grab and go food. Today, Britain’s sandwich industry is worth £8 billion and is still growing at 2% which 80 million more sandwiches a year.