Soak duck in cold water with juice of 1 lemon for 30 minutes before cooking. Dry thoroughly. Salt and pepper inside and out. Fill cavity with celery, onion, orange, apple and Worcestershire. Lay strip of salt meat over bird, secure with toothpicks. Place in heavy Dutch oven with 3 cm water in bottom. Bake covered at 160ºC or 1 hour, or until very tender. Baste often. Before serving remove salt meat; brown by removing cover and basting.