This year is the 250th anniversary of the sandwich. According to the British Sandwich Association, John Montagu, the fourth Earl of Sandwich, was playing cards when he requested meat between pieces of bread so he could easily eat without interrupting the game. From BBC News:
Foodsmith Sam Bompas said the Earl of Sandwich was eating with his fingers "when cutlery was de rigueur".
"Eating of record at the time was service á la française where all the food went on the table at the same time and there was an elaborate ritual of carving, aided by troops of servants," said Mr Bompas.
"What you have with the sandwich is the shock of informality. He was a daring man to eat in such a way coming from his social background."