Put the gammon in a large pan with the onion, sliced carrot, cinnamon stick, peppercorns and bay leaf. If your gammon is from the supermarket and wrapped in a plastic sleeve to help keep its shape, leave it on. It's heat resistant and won't harm you
Pour the cola in and bring to the boil
Turn down to low, cover but vent and let gently simmer for 2.5 hours, adding boiling water if the liquid level drops below the top of the gammon joint
Preheat the oven to gas 5 / 190C /375F and line a roasting tin with foil
Lift the gammon out of the pan and let settle on a plate while you discard the rest of the pan contents. You can take the plastic off at this point
Put the gammon into the roasting tin, then trim off some of the fat to leave an even layer. Score in a criss-cross / diamond pattern
Mix the glaze ingredients together and pour half over the gammon
Roast for 15 minutes then pour the remaining glaze over and roast another 15 minutes
Baste and roast a final 15 minutes
Take out of the oven and let rest in the tin for 10 minutes
Baste the gammon again with the tray juices before carving
