Place the gammon into a large, deep pan, and cover the joint in water. Bring the water to a boil, remove from the heat, then drain
Juice the Jaffa oranges
Put the gammon back into the (now empty) pan and cover it with Jaffa orange juice, then pour in some cold water until the liquid covers the gammon completely
Stud the onion halves with two cloves in each, then place in the pan with bay leaves. Cover the pan with a lid and bring the contents to a boil, then turn the heat down and let it simmer.
Gently cook the gammon for three hours, checking every so often to see if it needs extra hot water adding
Preheat the oven to 180°C
Carefully take the gammon from the pan, and place onto a roasting tin
Remove the skin, ensuring a thin layer of fat remains. Using a sharp knife, score the gammon with a criss-cross pattern, and stud each cross with a clove
Place the gammon to one side whilst you prepare the glaze. For this, just mix all the glaze ingredients together in a bowl until well combined. Using a spoon or spatula, spread the glaze generously all over the gammon joint
Put the gammon into the oven and roast for 45 minutes, spooning the glaze and juices over the gammon frequently throughout the cooking time, until it is golden-brown all over and cooked all the way through
