Wrap the gammon loosely in foil so that there is room for air to circulate
Place in a tin and cook for 20 mins per 450g (1lb)
Mix the mustard and honey together in a bowl
About 20 mins before the end of cooking remove the gammon from the oven and open up the foil. Remove the skin, if there is any score the fat in a diamond pattern then spoon the mustard and honey glaze all over it.
Increase the heat of the oven to 220C /425F / Gas 7 and return the gammon to the oven for the last 20 mins basting from the tin if it looks dry.
Once cooked remove the gammon from the oven wrap it back up in the foil and allow to stand for 15-20 mins before carving.