Place the gammon in a large saucepan. Add all the ingredients for the ham to the pan, adding more water if the ham isn't covered. Bring to the boil, before reducing the heat to a simmer and partially covering the pan. Cook for about 2 1/2 to 3 hours, approximately 1 hour a kilo simmering time, plus an extra 15 minutes.
When you are ready to glaze the ham, preheat oven to 440 degrees F (230 degrees C).
Remove the ham from the liquid and sit the ham on a board. Strip off the rind, and a little of the fat layer if it's very thick, and cut a diamond pattern into the remaining fat with a sharp knife in lines of about 3/4-inch apart. Stud each diamond with a clove. Put the jelly, cinnamon, paprika and red wine vinegar into a saucepan and whisk together over a high heat bringing it to the boil. Let the pan bubble away so that the glaze reduces to a syrup-like consistency.
Place a layer of foil over a roasting tray big enough to hold the ham. Place the ham on top of the foil. Pour the glaze over the clove-studded ham and then transfer it to the oven. Cook for about 15 minutes, or until the glazed fat is burnished. Allow the meat to rest in a warm place for at least 15 minutes before carving it.
Recipes from Feast by Nigella Lawson, published by Chatto and Windus