Mr Bompas added that he found it odd that the sandwich did not exist before the Earl of Sandwich ordered meat between slices of bread.

"Other people were probably eating in that way anyway but they were people who weren't written about," he said.

I think we can replace that 'probably' by 'certainly'. Given bread - which has been a basic foodstuff since crop farming got underway - and any ingredient of your choice, you only have three options: eat them entirely separately, put the ingredients on top for an open sandwich, or enclose the ingredient, as like as not to stop it falling off. The idea that we weren't doing all three from more or less the first time we had bread in seems unlikely, to say the least. As to the word 'sandwich' itself, the OED has much earlier uses as a kind of cord.

Now, if you mean identifying a point in time when a particular style of eating became acceptable to one specific class of people in one specific country, that's a different matter, but its a much smaller claim than inventing the sandwich.