The corned beef and beetroot butty. The ingredients are Sainsbury's prepacked corned beef (six slices), butter, Baxter's sliced beetroot in vinegar (drained), and - the hardest bit - the bread. I chose a thinly-sliced loaf made by our local baker Pete (he's been around forever, his loaf being a seeded job which he calls his "Cotswold Crunch"). The crust is pleasantly crunchy but the bread inside is soft.

The resulting butty was a bit of a masterpiece. I have two golden rules when making a sandwich: first, butter the bread generously right to the very edge of each slice. Second, the filling, if something meaty such as ham, roast beef, corned beef or chicken, must be exceptionally generous and multi-layered, and never underdo the mayo/horseradish relish or mustard. If egg mayo, the filling must be so excessive that it oozes out when you bite into the butty, such that it would be unwise to try to eat it whilst not sitting over your plate.

My favourite shop-bought sandwich is the spicy M&S "best-ever prawn." The last time I ate one al fresco in Truro, a bloody seagull came at me from behind and cleanly removed half of it from my clutches. A tragedy of Shakespearean proportions.