Boil the potatoes for 12-15 mins until tender, then drain and leave to cool a little. Cut the potatoes into thick slices. Mix together the yogurt, mustard and lime zest. Toss the potatoes with 4 tbsp of the dressing and 3 tbsp of the onion.

Put the turkey in a medium bowl and toss with the oil, then cook in a non-stick frying pan over a medium heat for 10 mins, turning at least once until the turkey is cooked through.

When you’re ready to serve, mix half the lettuce, watercress, half of the remaining onion and 1 of the peppers in a bowl. Top with half the potatoes, and slice and pile on half the turkey. Toss the avocado with a good squeeze of lime, then scatter half on top with half the grapes and half the walnuts. Spoon over half of the remaining dressing.

If packing this into lunchboxes, do the same with the remaining ingredients in the lunchboxes, but in reverse, so the green salad is at the top. Keep the dressing in a pot separately, to drizzle over just before eating. Will keep chilled for two days.