Line a salad bowl with leaves of lettuce. Place a layer of sliced potatoes on this; top with a layer of sliced tomatoes; sprinkle with quartered olives, sliced celery and flaked tuna fish.
Make a dressing by combining lemon juice, olive oil, chopped anchovy fillets and parsley. Season to taste with salt and freshly-ground black pepper and pour over salad. Just before serving, toss.