Britain’s first packaged sandwich was sold by Marks and Spencer in 1980 for 43p, and the first Pret A Manger opened six years later. It was a decade of economic transformation: city offices were replacing factories as engines of growth, and sandwiches were the fuel they ran on. Pret’s branches are now ubiquitous in the capital city. There are as many on London’s Borough High Street as there are in Wales. The rise of Pret has mirrored the rise of London and, until recently, they both seemed unstoppable.