Wash the duck inside and out, and pat dry with a paper towel.
Tie the legs firmly together with kitchen string.
Rub skin of duck with coarsely ground salt and pepper.
Place the duck on a wire rack over a roasting tray, and prick the skin all over. This will allow the fat to drain off.
Cook in the middle shelf of the oven for 1 hour and 20 minutes, frequently basting duck with own juices.
Remove the duck from the oven and set aside for 10 minutes to rest before carving.
Cook the port (optional), orange juice, orange zest, soy sauce, lemon juice, ground ginger and cherries in a medium saucepan over a high heat. (Reserve 2 tablespoons of the juice from the canned cherries!)
Bring to the boil, then reduce to a low heat, and simmer for 5 minutes.
In a separate small bowl, mix the reserved cherry juice with the cornflour. Stir into the sauce and cook for a further minute until the sauce thickens.
Serve the cherry sauce with the carved duck, boiled potatoes and young vegetables.