My Mum made this for us yesterday - delicious!
The duck was placed in a roasting pan on a trivet with half a lemon (use the other half for the apple sauce) in the cavity and covered with tin foil. She then roasted it in a low oven (gas mark 3 or 4) for about three hours, removing the foil for the last 20 minutes to crisp the skin. Mmmmm!
Bramley apple sauce
1 lb Bramley apples
1 oz unrefined sugar
4 tbsp water
juice of half a lemon
knob of butter
Peel and roughly chop the apples. Place in a pan with the lemon juice, water and sugar and stew (covered on a low heat) for about 15 minutes, stirring occasionally. You can then whisk or puree the sauce to the consistency you like, adding the butter to make it silkier and delicious.
If you have any left over this is great with pancakes or porridge the next day. Also (famously) goes well with pork.