Take the ham out of the fridge an hour before you start. Heat the oven to 160°C (140°C fan).
Cut through the skin around the shank end, about 10 cm from the bone. Slide your fingers under the cut edge and peel the skin away in one piece, leaving the fat behind. Trim the fat back to about 1 cm if it’s thicker than that.
Score the fat in a diamond pattern, cuts about 3 cm apart and going through the fat only, not into the meat. Press a whole clove into each intersection.
Sit the ham on a rack in a large roasting dish. Pour 2 cups of water into the dish — it stops the drips burning and keeps the oven humid. Cover loosely with foil.
Bake for 1 1/4 hours to warm the ham through, about 15 minutes per kilo.
Whisk the glaze ingredients together in a small saucepan and warm over a low heat until the sugar dissolves.
Turn the oven up to 200°C (180°C fan). Remove the foil and brush a third of the glaze over the ham.
Return to the oven for 30 minutes, brushing with more glaze every 10 minutes, until deep golden and sticky. Watch it in the last 10 minutes — it can catch quickly.
Rest for 20 minutes before carving, or cool completely if serving cold.