Mix the Mayonnaise and mustard and spread over the breads.
Wash, peel and cut strips of cucumber (the length of the bread). Cut a few radishes lengthways.
Take 4 slices of bread and top with a lettuce leaf. Then arrange the salmon over the lettuce and drizzle with a little lemon juice. Season with pepper.
Top each slice with 2 slices of cucumber and 3 slices of radish. Cover with the remaining bread slices.