Healthy salad Niçoise

Name: Healthy salad Niçoise
Ingredients: 200g new potato, thickly sliced; 2 medium eggs; 100g green bean, trimmed; 1 romaine lettuce heart, leaves separated and washed; 8 cherry tomatoes, halved; 6 anchovies in olive oil, drained well; 197g can tuna steak in spring water, drained; 2 tbsp reduced-fat mayonnaise