I found this in a search: (I could not believe that one man 'invented' putting meat or cheese on bread...it is just too obvious)

"One of the most charming characters in culinary history was John Montague, the 4th Earl of Sandwich. It is known that after the Earl retired from a glorious naval career (among other things, he is credited with having discovered the Hawaiian Islands), he de- voted most of his life to playing cards. It is said that he was so addicted to the pleasures of gambling that he refused to leave the gaming table even for meals. According to a well believed story, it was this habit that led the Earl to teach his servants how to put meat, cheese or other ingredients between two slices of bread and thus created "the sandwich".

This may make for a great story, but the realities of the Earl's life tell us that it could not possibly have been true. Due to a severe wound incurred during a naval battle when he was only 17 years old the Earl had a gastro-intestinal disorder that allowed him to subsist only on liquids. The Earl could not have eaten a sandwich even if he had wanted to.

There is, however remote it may be, a possibility that the Earl actually did contribute to the popularity in England of the creation that even today carries his name. In 1748, the Earl visited France, there to discover that French landowners were responsible by law for providing their field workers with a noontime meal. Because it was convenient for everybody, the most common meal sent out to the fields was made by placing meat, potatoes, vegetables and sauce between two thick slices of bread. Some speculate that the Earl was so impressed by the economy of such meals that on his return to England he began to feed them to his own workers. "