Cook the beans in boiling salted water until tender but still with a little bite. Drain and refresh under cold running water then drain again.
Tip the tomatoes and their oil into a bowl, add the olives and mix gently.
Arrange the lettuce on serving plates and top with the tomato olive mixture, saving the juice.
Drain the tuna and divide the chunks among the tomato and olives, then strew with the drained beans.
Use the reserved tomato juices to make a dressing with the extra virgin olive oil, lemon juice, salt and sugar. Whisk together then pour over the salad.
Peel and quarter the eggs and add to the salad along with the croutons, anchovy fillets ( if using) and basil leaves. Serve immediately.