Place ham fat side down in a shallow tin. Pour cola into tin 1.25cm deep. Bake 2 to 3 hours or until ham can easily be pierced with a fork, basting with cola every 15 minutes. centre of ham will read 60 degrees C on a meat thermometer. Remove ham from tin and cool.
Increase oven temperature to 190 C / Gas 5.
Cut away the rind with a sharp knife. Combine sugar, mustard, breadcrumbs and enough cola to form a thick paste. Spread paste over entire ham. Place ham on roasting rack in oven and bake 45 minutes longer, basting every 10 minutes, until mustard paste has melted into a dark glaze. Let stand at room temperature 30 minutes before slicing.