Place the turkey in a roasting tin and starting at the neck of the bird, slide your hand between the skin and the breast meat to loosen it. Take some of the softened butter and rub it onto the breast meat (under the skin). Rub some more of the butter over the top of the skin. Season well with salt and pepper. Place the 2 lemon halves in the cavity of the turkey - these will help to keep it moist.
Roast for 30 minutes until golden brown all over, then remove and brush with softened butter. At this stage, reduce the oven temperature to 180 degrees C.
Continue to baste every 30 to 40 minutes with softened butter or spoon over the turkey juices from the roasting tin, until the turkey is cooked and the juice from the thickest part of the leg run clear (about 3 1/2 more hours). Transfer to a serving platter but cover with foil to keep warm.
Place neck and giblets in a separate pot along with celery stalk, carrot and herbs, then add enough water to cover. Bring to a boil and simmer for 15 minutes. Pour this through a sieve, discarding the solids.
Pour the sieved turkey stock into the roasting tin and stir to scrape up the delicious brown bits. Add a splash of red or white wine for extra flavour. Pass through a sieve again and reheat before serving.