To make the stuffing, melt the unsalted butter in a saucepan and add the bacon, shallots, celery and rosemary. Cook gently with the lid on for about 10 minutes, until the vegetables are very soft, but not coloured. Add the cranberries and half the cider and turn up the heat a little. When the liquid has reduced to a third of its volume, set it aside to cool. Mix in the nutmeg, allspice, some salt and pepper, the walnuts, orange zest, sausage meat and egg, then fold in the breadcrumbs.
Preheat the oven to 240°C/475°F/gas 9. Pat the turkey’s skin dry with kitchen paper, then stuff the neck end with half the stuffing. (You can cook the remaining stuffing separately or use it to make sausage rolls on Boxing Day.) Rub the bird with the softened butter and season well. Place in a roasting tin, cover with foil and pop in the preheated oven. After 15 minutes, turn down the heat to 150°C/300°F/gas 2. Baste, then roast for another 2 to 2¾ hours.
Remove the foil 1 hour before the end of cooking time. To check the bird is cooked, stick a fork into the thickest part of the thigh – the juices should run clear. Remove the turkey from the oven, lift out of the tin, cover with foil, then leave to rest for at least 1 hour, preferably 2 hours for bigger birds.
Increase the oven temperature to 200°C/400°F/gas 6. Skim off the fat in the tin and use it to roast your potatoes. Add the rest of the cider to the meat juices in the tin, along with the meat off the turkey wings and enough stock to cover the bottom of the tin. Stir in the cornflour, dissolved in a little water, and simmer on the hob until thickened. Sieve into a jug and serve with your turkey, stuffing and some roast potatoes.