Cranberry-glazed roast ham

Soak the gammon joint in cold water overnight, then drain it, discarding the water. Weigh the gammon to calculate the cooking time - it will take 25 mins per 500g, plus 20 mins (so a 2kg joint will take 2 hours). Place the gammon in a large saucepan and add the bay leaves, onion, celery and carrots to the pan, then cover the gammon with cold water. Bring to the boil, then reduce the heat and cover the pan. Start the timing from the moment the gammon comes to the boil. Simmer the gammon for the calculated time. Remove pan from the heat and carefully lift out the gammon, reserving cooking liquor. Remove the string. Cut the skin off the gammon, leaving just a thin layer of fat. Score through the fat in a diamond pattern using a small, sharp knife. Press cloves, if using, into the fat and the gammon. Mix together the cranberry sauce, Demerara sugar and vinegar. Spread mixture over the top of gammon. Place gammon in a roasting tin and spoon some of the cooking liquor around it. Set the oven to 190°C (375°F, gas mark 5). Bake the gammon in the centre of the oven for about 20-30 mins, or until the topping is bubbling and has started to crisp. Remove it from the oven, transfer to a warmed serving plate and keep it warm until serving.