Pre heat oven to 200 degrees C. Peel and cut the potatoes into even size pieces, about 3 pieces per potato. Place in cold salted water and bring, covered to the boil. Boil for 10 minutes. Drain off the water and shake about in the saucepan to roughen up and crush the edges. Sprinkle over the cornmeal and shake to evenly coat the potatoes. Heat the oil or dripping in the roasting tin until very hot before adding the potatoes. Turn to coat well in the oil and roast about 45 minutes, stirring a couple of times until the potatoes are golden and crispy. Sprinkle with sea salt flakes before serving. Make sure the potatoes are served piping hot or maintain crispness.