Leg of lamb with red wine sauce

Preheat the oven to 160 ºC (320 ºF). Blend all the ingredients for the marinade in a large glass, ceramic or plastic container and marinate the lamb for 4-6 hours or overnight. Pat dry with paper towelling and season well with salt and pepper. Arrange a few orange slices on top of the meat. Place on the rack of an oven roasting pan and roast 25 minutes for each 500 g plus 25 minutes extra. Baste frequently with the marinade. Transfer the meat to a serving platter, cover and leave to rest in the warming drawer for about 10 minutes before carving. Meanwhile pour the remaining marinade into the roasting pan and bring to the boil. If necessary, thicken the sauce with cornflour blended with a little water. Serve the leg of lamb with the sauce and a selection of vegetables.
Serves 6-8.