Preheat the oven to 200°C.
Place the pork on a rack in a roasting pan.
Mix the maple syrup, mustard, vinegar, soy sauce in a small bowl, then brush the mixture evenly over the pork joint.
Pour some water or white wine into the pan (underneath the pork).
Roast the pork for 20 minutes or until the skin look crispy and brown.
Coat the pork again with the glaze then cover the dish with foil.
Turn down the oven temperature to 175C and roast for about 1.5 hour (35 minutes per 500g).
Remove from the oven. If the skin is not crunchy enough, turn up the temperature and cook for another 5 minutes or so.
Rest the pork, covered with foil, for about 10 minutes before carving. Meanwhile, make some gravy from the cooking jus and any leftover glaze.