To make the cocktail sauce, Combine the mayonnaise, tomato sauce, lemon juice and Tabasco sauce in a bowl. Season with salt and black pepper.
Peel and devein the prawns, leaving some of the prawn tails intact for presentation.
Arrange the lettuce in four serving glasses or bowls and divide the prawns among the glasses. Spoon over alittle of the cocktail sauce and sprinkle with apinch of cayenne pepper. Serve with lemon wedges.