1. Put the gammon in a large, deep pan and cover with water. Bring to the boil, remove from the heat and drain.
2. Return the gammon to the pan, and then pour in the orange juice. Pour in enough cold water to cover the gammon completely.
3. Push two cloves into each onion half and add to the pan along with the bay leaves. Cover with a lid and bring gently to the boil (this will take about 30 minutes), skim the surface and then reduce the heat to a simmer. Cook gently for 2 ½ hours, adding more hot water to the pan as necessary.
4. Preheat the oven to 180°C/fan oven 160°C, 350°F/Gas 4.
5. Remove the gammon from the pan and sit onto a chopping board. Using a long knife remove the skin, leaving behind a thin layer of fat. Score the gammon in a diamond pattern with the tip of a knife. Place a clove in the middle of a few of the diamonds. Sit the gammon into a roasting tin.
6. Mix together the marmalade, honey and mustard. Spoon or brush the glaze evenly over the gammon.
7. Roast the gammon in the oven for 45 minutes, basting frequently with the glaze and pan juices, until the gammon is cooked through and golden-brown all over.