1. Mix together the orange, ginger, marmalade and seasoning.
2. Coat the pork with the marinade and leave in the refrigerator for 4-5 hours or overnight.
3. Place the pork in the roasting pan in a preheated oven 190°C (375°F) gas mark 5.for 30 minutes per 500 g plus an extra 30 minutes.
4. 15 minutes before the end of the cooking time, spoon over the remaining marinade from the marinating dish. Return to the oven.