For the gammon, place the gammon into a large, deep pan and cover with water. Bring to the boil, then remove from the heat and drain.
Return the gammon to the pan, then pour in enough orange juice to cover half of the gammon. Pour in enough cold water to cover the gammon completely.
Push two cloves into each onion half and add to the pan along with the bay leaves. Cover with a lid and bring to the boil, then reduce the heat to a simmer. Cook gently for three hours, adding more hot water to the pan as necessary.
Preheat the oven to 180C/360F/Gas 4.
Remove the gammon from the pan and place into a roasting tin. Remove the skin, leaving behind a thin layer of fat. Score the gammon in a diamond pattern with the tip of a sharp knife. Stud the centre of each diamond with a clove.
For the glaze, mix together all of the glaze ingredients in a bowl until well combined. Spoon the glaze evenly over the gammon.
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.
Set aside to rest, then carve into thick slices to serve. Alternatively, the gammon can be eaten cold. Serve with apple compote and pickled red cabbage.