Preheat oven to 150°C.

Remove skin off the ham by using a small knife to cut through the skin around the top of the ham handle. Then on the side where the cut meat is, run the knife between the skin and the fat, using your fingers to separate it even more. Leave as much fat as possible.  Start in a corner and peel back the skin.

Use a small, sharp knife to score a diamond pattern over the fat and set the ham aside to rest at room temperature for 1-2 hours.

Line a baking tray or dish with baking paper,  place ham on tray, pour 1/3 cup of water into the base of the pan and cover the ham loosely with tin foil and bake for 30 minutes.

To make glaze, heat the butter in a small saucepan over medium heat until golden brown. Add in the sugar, honey, mustard and cinnamon, stirring until the sugar has dissolved.  Set aside to cool to room temperature.

After 30 minutes, remove ham from the oven and increase oven temperature to 220°C. Discard the foil and pour 1/3 of the glaze over the ham, brushing in between the cuts to evenly cover. Return to the oven and bake uncovered for 15 minutes.

Remove from oven, brush with another third of the glaze and some of the pan juices, and bake a further 15-30 minutes until the edges start to crisp and go a dark brown, glazing every 15 minutes.

Allow ham to rest 20 minutes before serving.  Mix any remaining glaze with pan juices and pour over ham once on the table.