Put the eggs in a small pan, cover with cold water; bring to boil. Boil for 7 mins; drain, rinse in cold water, tapping shells all over. Peel away the shells. Cut in half and cool. Beat the mayonnaise, vinegar and mustard together.
Divide the lettuce, watercress, tomatoes and cucumber between four plates. Arrange the eggs on top and spoon over the mayonnaise. Chill until ready to serve. Dust the eggs with paprika before serving with bread and butter.