Drain the cans of prawns and asparagus tips, reserving the liquid.
Slice the olives.
Heat the olive oil and fry the spring onions for 3 minutes; add the reserved liquid, tomato puree, lemon juice, sugar, salt, black pepper, tomato ketchup, Worcestershire sauce and Tabasco.
Stir and simmer gently for 5 minutes. Remove from the heat, add the prawns, almonds, and olive slices, reserving some for garnish. Mix and cool.
Before serving, divide the lettuce into six portions, arrange the prawn mixture over them and garnish with the reserved sliced olives and asparagus tips.