Preheat your gas barbecue for 10 minutes for indirect cooking.
Using a sharp knife cut the skin of the ham. Cut directly down the centre and around the knuckle so the skin is easy to remove later.
Place the ham in the center of the barbecue and set the control knobs to the roast setting.
Cook the ham for 45 minutes or until the skin is starting to separate at the centre.
Make the glaze while the ham is cooking. To make the glaze, place all the glaze ingredients into a medium saucepan. Cook the glaze on the side burner or stove top over a high heat until just boiling. Then reduce the heat to low and simmer for 10 minutes making sure to stir the glaze every few minutes to prevent the bottom from burning.
Remove the glaze from the heat and set aside until needed.
Remove the skin from the ham and score the fat in a diamond pattern. Make sure not to cut too deep as you only want to allow the fat to render and not the flesh to dry out.
Liberally apply a layer of the glaze over the ham. Continue to cook the ham for another 15 minutes.
After the 15 minutes has passed apply another coating of the glaze. Cook for another 15 minutes or until the ham has reached an internal temperature of 60C.