Place ham in a large stockpot and cover with cider. Leave in a cold place to soak overnight.
Heat the stockpot over medium high heat. Add the peppercorns and bay leaf and bring to the boil. Reduce heat and simmer for 30 minutes per 450g (1 lb). Remove from heat.
Preheat oven to 220 C / Gas mark 7. In a small bowl, mix the sugar and mustard.
Remove the leg from the stockpot, carefully peel off the skin and score diamond shapes into the fat with a sharp knife. Stand the ham in a roasting tin with a small amount of the cider to cover the bottom of the tin. Spread the sugar and mustard mixture over the fat on the ham. Press a clove into the corner of each diamond shape.
Roast the ham in preheated oven for 20 to 30 minutes until the fat is crisp and golden. Remove and allow to cool before carving.