1. Cook green beans until they are tender-crisp; drain; and immediately put into cold water to prevent further cooking. Drain again and pat dry.
2. For vinaigrette, whisk all ingredients together in a small bowl.
3. Toss beans, potatoes, and artichokes in vinaigrette. Let stand 1 hour.
4. Wash lettuce and dry; line large, shallow bowl with the lettuce.
5. Spoon bean mixture onto lettuce.
6. Arrange tomatoes, tuna, and eggs on top of salad.
7. Drizzle any remaining vinaigrette on top.
8. Sprinkle with anchovies, capers and olives.