Preheat the oven to 200C/400F/Gas 6.
Cut the potato into chips and drizzle with two tablespoons of oil. Place on a baking sheet. Cut the tomato in half and sit it on the side of the baking sheet. Bake for 30-40 minutes, or until the chips are golden-brown and crisp and the tomato is softened.
Heat one tablespoon of the oil in a frying pan. Season the gammon with salt and freshly ground black pepper and fry on both sides for 5-6 minutes, or until completely cooked through. Set aside to rest in a warm place.
Heat the remaining oil in a frying pan and fry the eggs until the yolk is just set.
To serve, place the gammon onto a plate with the chips and tomato. Top with the eggs.