Weigh your piece of gammon, or make a note of the weight printed on the label. Put the gammon, ginger ale, beer, star anise, bay leaves, cloves, onion, cinnamon, mace and peppercorns into a large, deep pot. Add enough water just to cover the gammon. Bring to the boil, then turn down the heat so that the gammon cooks at a lively simmer. Partially cover the pot with a tilted lid. If you’re using a boneless gammon, cook the meat for 30-40 minutes per kilogram. If you’re using a gammon with a large bone, cook it for 45-55 minutes per kilogram, or according to the instructions on the wrapping. Check the pot now and then, and top up with more water if necessary.

Turn off the heat and leave the gammon in the liquid to cool completely. (It’s a good idea to boil the gammon the day before, and to leave it overnight to cool.)

Preheat the oven to its hottest setting (220-240ºC.) Pour the Coca-Cola into a large, fairly shallow pan (a wok is ideal), turn on the heat and bubble briskly until the liquid has reduced by half. Whisk in the Dijon mustard, the mustard powder, the sugar and the coffee powder. Turn up the heat and boil fast, stirring often, for 5 to 7 minutes, or until the liquid has reduced and is slightly syrupy. At this stage, you should be left with about 200 ml of liquid. Remove from the heat and stir in the lemon juice and brandy.

Fish the gammon out of its cooking liquid, pat quite dry and place in a roasting pan. Carefully peel away the rind and discard. Using a sharp knife, score the top of the gammon in a diamond pattern. Stud the gammon with whole cloves.

Pour the glaze over the gammon and place the roasting pan in a blazing hot oven. Cook for 20-30 minutes (how long this takes will depend on the heat of your oven), basting the meat every four to five minutes by scooping the glaze off the bottom of the pan and trickling it all over the top and sides. The glaze will thicken and reduce as time goes by: watch it like a hawk, as it burns easily. When the gammon has a mahogany-brown sticky crust, and there is just a little glaze left in the bottom of the pan, remove it from the oven. Using a pastry brush, paint any remaining glaze over the top and sides of the gammon. Set aside to rest for ten minutes, then serve hot with boiled new potatoes and a green salad. If you’re serving this cold, store it, uncovered, in the fridge, for up to four hours.