Preheat the oven to Gas Mark 4, 180°C, fan160°C. With a sharp knife, cut in a straight line through skin round the ham shank, 7cm (3in) from end. Carefully insert your thumb under the cut edge facing away from shank to make an air pocket between skin and fat. Start to pull skin away from fat towards the large end of ham, away from the shank. Run one hand under skin and pull it away with the other hand so it comes off in one piece. Lightly score the fat into a diamond pattern. Do not cut through to the meat, or the fat will fall off during cooking. Combine all remaining ingredients except cloves, and mix until smooth. Place a clove in centre of each diamond, then spread half the glaze over ham, avoiding the shank. Place ham on a rack in a large roasting tin and pour 500ml (17fl oz) water into the tin. Lightly cover the ham with foil, securing the foil to edges of the tin. Cook for 50 minutes, then take out of the oven and increase oven temperature to Gas Mark 6½, 210°C, fan190°C. Remove foil, brush over the remaining glaze without knocking off the cloves and return to oven uncovered. Cook for a further 25 minutes or until the surface of the ham is caramelised ant the meat is cooked through. Remove from the oven and set aside to rest for at least 15 minutes before carving. While the ham is cooking, make the cherry relish. Place all the ingredients in a pan and stir over a high heat until the sugar has dissolved. Allow to come just to the boil, then reduce the heat and simmer for 40-45 minutes, or until most of the liquid has been absorbed. The small amount of the relish left will thicken on cooling, making it more like a glaze. Serve it warm, or at room temperature, to accompany the ham.