As the nation’s favourite lunch chain removes its £4 ham sandwich, the classic jambon beurre, from its chiller units over a shortage of imported cornichons, James Moore reveals what it tells us about the UK’s fragile supply chains P ret a Manger is in quite the pickle. The sandwich chain whose price increases in recent years have become increasingly bold has now removed its most popular sandwich, the jambon beurre , from its shelves. For the uninitiated, that’s a ham and pickled mini-cucumber