Preheat the oven to 180°C (350°F)
In a saucepan place the honey, maple syrup, mustard and Guinness and bring to boil, reduce to a third.
While the glaze is cooling, remove the skin from the leg of ham by forcing your finger between the rind and the fat, and simply pull off (try to keep as much of the fat on as possible). Use a sharp knife to cut through the skin at the shank end leaving the shank end with a good 5cm (2 inch) skin at the end to help hold the ham
Using a sharp paring knife score across the fat very lightly at 2.5 -3cm intervals, cutting just through the surface of the fat, not into the meat (about 3mm). Score in the opposite direction to form a diamonds or square pattern, decorating the ham by studding with cloves in the center of each diamond or square.
Place the ham in large baking dish. Spoon the glaze all over the ham, and using a pastry brush cover any areas which aren’t covered in glaze.
Bake for 2-3 hours.
Every 20 minutes, open oven and spoon the glaze which will have accumulated in bottom of tray, all over the ham.