Place the ham cut side down onto a sheet of aluminium foil. I like to put the shiny side up.
Mix together the brown sugar, apricot jam and mustard powder in a small bowl. Brush onto the ham using a pastry or barbecue brush. Reserve any leftover glaze. Enclose the foil around the ham and place on a baking tray.
Roast for 2 hours in the preheated oven. Apply the remaining glaze 20 minutes before the ham is done.