Heat oven to 190C/fan 170C/gas 5. Wash and dry the turkey, removing any feathers. Pull out the giblets and the neck, then set aside.
Lift up the skin that covers the neck opening, then stuff the stuffing up and under the skin, securing it tightly underneath with a skewer or two cocktail sticks. Weigh the stuffed turkey, then calculate the cooking time, allowing 40 mins per kg (20 mins per lb).
Put the leeks and carrots along the bottom of a roasting tin in a single layer – this will make a trivet for the turkey to sit on and add flavour to the gravy. Add the neck to the tin. Sit the turkey on top and coat the breast all over with butter.
Pour in the cider, cover with foil, then roast according to your timings. Keep checking the tin – if the vegetables look like they’re burning, add a splash of water or cider. At 30 mins before the end of cooking, remove the foil and season generously.
To test that the turkey is ready, pierce the thigh through its thickest part; the juices should run clear. Take the turkey out and leave to rest, covered with a clean tea towel. Can leave to rest for up to 1 hr.
Now make the gravy. Drain the fat and juices from the tin into a jug, discarding the veg and the neck. Place the tin over a flame, then pour in the cider, scraping up the flavour-filled crusty bits with a wooden spoon.
Reduce the cider by half, then strain into a saucepan (this will save you hob space later).