Preheat the oven to 200°C, fan 180°C, gas 6. Make the stuffing according to the pack instructions and stuff the neck end of the turkey, pulling the excess skin around the stuffing and tucking it underneath the turkey. Use a cocktail stick to secure if necessary.
Evenly rub the butter over the turkey, then tie the legs together with kitchen string. Arrange the bacon rashers over the breasts.
Weigh the turkey and calculate the cooking time based on 20 minutes per kilogram, plus 90 minutes.
Put the turkey on a rack in a roasting tin. Cover with foil and roast for the calculated cooking time. Remove the foil for the last 40 minutes to brown the top