Put your potatoes on to boil, they should take 20 or so minutes, depending on their size. When the water is boiling, add your eggs and boil for 7 minutes, then take out and let cool in a bowl of cold water. Peel when cool and set aside.
Arrange your washed lettuce on a large serving plate.
With 10 minutes to go on your potatoes, add your beans to the boiling water. After 10 minutes, drain water and season pots and beans with salt and pepper and a glug of extra virgin olive oil. Set aside to cool off a little.
Drain the oil from the tuna, and whisk with the vinegar and salt and pepper. This is your dressing.
Start compiling the salad. Quarter your eggs and arrange on top of the lettuce. Do the same with the tuna, olives, red onion, then the halved potatoes and green beens. Drizzle the dressing over and serve, ideally with a crusty baguette and a cold glass of white wine. (Feel free to wear a beret and smoke a fag afterwards with an insouciant air, if the mood takes you...)