1. Soak the ham in cold water for 48 hours (or 24 hours if you like a saltier ham), changing the water every 8 hours. Put all the ingredients, except those for the glaze, into a large pan, on the stove but off the heat, adding fresh water until the ham is covered.
2. Turn on the heat and bring to the boil, then turn down to a simmer and partially cover the pan. Cook for about 3 ½ hours. (This may not seem long for a big ham, but as it will carry on cooking as it cools, and this is going to be eaten cold, I don’t want it overcooked. Nor do you.)
3. Preheat the oven to 400°F. Lift the ham gently out of the hot liquid, sit it on a board and let it cool slightly, not too much but just so that you can touch it without burning yourself.
4. With a sharp knife, strip off the rind, and a little of the fat layer if it’s very thick, but leave a thin layer of fat. I love this work: it is peculiarly gratifying seeing the hot blubbery fat slither off. Use the same knife to score a diamond pattern on the remaining fat on the ham, in lines about ¾ inch apart. Stud the points of each diamond with a clove.
5. Put the cranberry or red currant jelly, cinnamon, paprika and red wine vinegar into a little saucepan and whisk together over a high heat, bringing it to the boil. Let the pan bubble away, for about 5 minutes, so that the glaze reduces to a syrupy consistency that will coat the fat on the ham.
6. Now sit the ham in a roasting pan lined with aluminum foil, as the sugar in the glaze will burn in the oven as it drips off. Pour the glaze over the diamond-studded ham, then put it in the oven for about 15 minutes, or until the glazed fat has caught and burnished. Take the ham out of the oven and sit it on a wooden board to cool (2-3 hours) before you carve it.