Fill a large pan with water and add the bay leaves, carrot, celery, onion and octopus. Bring to the boil and simmer for about one hour, or until a sharp knife can pass through the flesh of the octopus easily.
Take the octopus out of the water and clean it again. Peel off the outer skin and remove the central eye. If necessary wash it again. Chop the flesh into small pieces.
Meanwhile, boil the potatoes. Drain and peel them and cut into slices.
Mix together the potato slices and octopus cubes. Season with salt and freshly ground black pepper to taste, then drizzle with the lemon juice and a generous helping of olive oil. Mix in the chopped parsley and serve.