Remove the parsons nose from the bird then stand the bird on its neck end, using a sharp knife carefully cut one side of the spine all the way down. Turn bird over, breast side up and press hard to squash bird flat. Place the bird on the lined roasting tin. The natural fats will cook it. Place in the pre heated oven at 200 degrees celsius or gas mark 5 and cook for 45 minutes- one hour or until the juices run clear in the leg or a thermometer reaches 73 degrees and stays at that for 2 minutes. Rest for 15 minutes then serve with optional seasoning.