Place the whiskey in a pan with the maple syrup, redcurrant jelly, balsamic vinegar and ground allspice. Bring to the boil and simmer for about 10 minutes, until slightly thickened. Stud the ham with the cloves and place in a large roasting tin with a little water to prevent the bottom from catching and burning. Brush a layer of the syrup all over the ham, reserving the remainder. Cook for 1 hour, brushing over another layer of the glaze every 15 minutes, until it’s all gone. Remove the cooked ham from the oven, transfer to a serving platter and leave to rest for 15 minutes.