1.Cook potato and beans, separately, until tender. Rinse under cold water, drain. Cool.
2.Combine potato and beans with tuna, tomato, egg, olives and parsley in medium bowl.
3.Pack salad in lunchbox, refrigerate. The next day, pack lunchbox and lemon slice with a freezer brick or frozen drink.
The night before, prepare the salad and keep, covered, in the refrigerator.Note