1. Place your gammon in a large lidded saucepan and cover with cold water. Place on a high heat and bring to the boil. Drain the water from your saucepan and replace with fresh cold water.
2. Bring to the boil once more before turning down the heat and simmering for 20 minutes.
3. Whilst your gammon boils make your glaze. In a pestle and mortar grind together your cinnamon, nutmeg, salt, pepper, and sugar. Transfer to a bowl and drizzle in your black treacle and mustard. Mix well.
4. Remove the gammon from the water and set to one side to cool.
5. Heat your oven to 200°C.
6. Score the fat of your gammon into diamond shapes and push a clove in to the center of each cross.
7. With a soft pastry brush paste your glaze all over your gammon before roasting in your oven for 10 minutes.
8. After 10 minutes open your oven and baste any juices in your tray back over your gammon. Roast for a further 10 minutes.
9. Rest your gammon on the side for 15 minutes before carving and pour any juices from your tray in to a jug and serve on the table, or pour over for extra sticky slices.