Plate Nappies

Bill writes: I need some help from British restaurant-goers here. When you take delivery of a meal in a low- to middle-range restaurant, it's odds-on that it will be delivered on a napkin on a plate. See illustrative photograph below.



You'll find them under sandwiches, under cakes, under bowls of soup. What's its purpose? British plate-napkins are a mystery to me, like bidets. I don't know what I'm supposed to do with them. I'm afraid to use them, and even more afraid to leave them alone. The thing is, look at that napkin. The sandwich was great, I'll grant that. It was a tuna melt. But that means the filling melted right out of the sandwich and onto the napkin. In the case of a cake, the frosting is all over the napkin. Bowl of soup? Soup stuff. You get the idea. So should I use the napkin? Is it there to wipe my face with (or more accurately to transfer tuna melt/cake frosting/soup from the plate to my face with)? Is it to keep the plate separate from the food, like some kind of low-tech thermal insulation? Or is it to make certain that tiny, wet, sticky, torn bits of blue paper from the napkin leech onto my tuna melt sandwich, thereby ensuring I'm getting a bit of color fibre into my diet?

As my friend Barbara would ask, "What's the deal with that?"