According to the Royal Society of Chemistry (RSC) the cheapest lunchtime meal in Britain is the toast sandwich.

(This shouldn’t be confused with the toasted sandwich, or toasty. A toast sandwich, popular in mid-Victorian times, consists of two slices of bread around a slice of toast. The meal, which will cost you 7.5p to make, was first promoted by Victorian food writer Mrs Beeton.

Here is the recipe:-
Ingredients
3 slices of bread
Butter
Salt and pepper
Method

1. Toast a thin slice of bread.
2. Butter two slices of bread and sprinkle with salt and pepper to taste.
3. Place the toast between the two slices of bread-and-butter to form a sandwich.

4. Eat.
Bon appetite!)