Preheat the oven to 200°C.
Loosen the skin on the turkey crown by carefully pushing your fingers between the skin and meat.
Mix thyme with softened butter and smear the mixture underneath the turkey skin.
Arrange orange slices under the skin and place an orange half and trimmings in the cavity.
Place turkey in a roasting tray, rub with oil, season, and roast for 1.5 to 2 hours.
Squeeze the remaining orange juice over the turkey 15 minutes before the end of cooking.
Rest the turkey on a platter for 30 minutes while reserving the tray juices.
Skim fat from the tray juices and heat the remaining liquid in a saucepan.
Whisk in flour, port, and stock, then simmer until thickened.
Add Worcestershire sauce, soy sauce, and any rested meat juices before seasoning and serving.