When you get your turkey, remove the giblets, which should be in the body cavity, and place the uncovered turkey on a plate in the lowest part of the refrigerator. Make sure you know how much it weighs so that you can calculate the cooking time – the timings given here are for a 14 lb (6.5 kg) bird. Late the night before, take it out of the fridge so that it will be at room temperature by the time you cook it. Try, if possible, to get a fresh bird. However, if you can only buy a frozen one, or if it's more convenient to do so, try to buy one that has been frozen without added water, then don't forget to allow plenty of time for it to defrost slowly and completely.
Stuff the turkey with your chosen stuffing – the quantity of stuffing will be the same whatever the size of your turkey. Place about two-thirds in the neck end between the flesh and the skin, then tuck the neck flap under the bird's back and secure it with a small skewer. Place the rest of the stuffing in the body cavity – there's no need to pack this in tightly. Note that it is only dangerous to stuff the body cavity if either the turkey or the stuffing is not defrosted properly, because the heat will not penetrate it quickly enough. If both are at room temperature it is perfectly safe. Spread 6 oz (175 g) of softened butter all over the bird.
Lay about 8 oz (225 g) of streaky bacon rashers over the breast of the bird, overlapping slightly, then season with freshly milled black pepper and a little salt.
Arrange two large sheets of foil across your roasting tin, one widthways and the other lengthways. Lay the turkey on its back in the middle of the foil then loosely wrap it: the parcel must be firmly sealed but with room for air to circulate around the turkey, creating 'an oven within the oven'. Place in a pre-heated hot oven, gas mark 7, 425°F (220°C), for 40 minutes – this initial blast is so that the heat gets right into the turkey and the stuffing very quickly. Then reduce the oven temperature to gas mark 3, 325°F (170°C) for 3½ hours.
After this time, remove the turkey from the oven, uncover it and discard any excess foil. Baste with the juices then increase the oven temperature to gas mark 6, 400°F (200°C). Cook the uncovered turkey for a further 40 minutes – once the bacon on top of the turkey has browned you can push it down into the tin to allow the breast to get a final browning.
After the final 40 minutes, remove the turkey from the oven. Pierce the thickest part of the leg with a skewer then press the skewer against the leg to see if the juices run clear without any trace of pink – if the juices are clear, the turkey is cooked. You can also give the legs a little tweak – if they feel like they've got some 'give' in them, then the turkey is done. Cover it loosely with foil and allow it to rest for about 45 minutes before serving – it will be fine at kitchen temperature.