Bring a large pan of water to the boil.
Add the potatoes and the eggs, and
cook for 7 mins. Scoop the eggs out of
the pan, tip in the green beans and cook
for a further 4 mins. Drain the potatoes,
beans and eggs in a colander under cold
running water until cool. Leave to dry.
Peel the eggs and cut into quarters.
Arrange the lettuce leaves in 2 shallow
bowls. Scatter over the beans, potatoes,
tomatoes and egg quarters. Pat the
anchovies with kitchen paper to absorb
the excess oil and place on top.
Flake the tuna into chunks and scatter
over the salad. Mix the mayonnaise and
1 tbsp cold water in a bowl until smooth.
Drizzle over the salad and serve.