Mix all of the glaze ingredients in to a thick paste.
Preheat the oven to 200C. Line a large roasting tray with baking paper.
Carefully remove the skin from the ham using a small blade knife, avoiding removing any of the fat layer. Using a sharp knife, score the fat in parallel lines about a centimetre apart (or in a criss-cross) pattern. Brush with a third of the glaze.
Place in the oven and bake for 15 minutes.
Remove the ham from the oven and brush with another third of the glaze. Return to oven and bake for 10 minutes. (note: If the ham glaze colouring is uneven turn the dish around, in case there are hot areas in your oven)
Remove ham from the oven and brush on the remaining glaze. Bake for a further 10 minutes, or until light golden brown all over.