And there you have it, my favourite, plain and simple: egg and tomato. Of course you have to have bread which is no great problem today.
Today the egg and tomato sandwich has perhaps another name. We could call it the “Isolation sandwich”. You have the bread at home in the freezer for emergencies. A box of eggs is also something you can store for some time. The tomatoes could present a problem, so keep a tube of tomato ketchup in the fridge in case the tomatoes are not available or are too old to use.. I like my eggs with black pepper.
I wonder how the Earl of Sandwich managed without a fridge.