Shred a gem lettuce heart and pile it into a couple of chilled glasses. Peel and dice a cucumber and add it to the lettuce. Mix 4 tablespoons of decent mayo with 2 heaped teaspoons of Cornish Ketchup Original and a good shake of Tabasco. Toss with 250g plump peeled prawns, a squirt of lemon juice and pinch of smoked paprika or cayenne pepper. Pile the dressed prawns on top of the lettuce with some sliced avocado and serve with a wedge of lemon.