“One must start from the general premise that the protection of the child’s welfare implies at least the protection of the child’s life. I state this as a general and not as an invariable premise because of the possibility of cases in which a court would not authorise treatment of a distressing nature which offered only a small hope of preserving life. In general terms however, the present state of law is that an individual who has reached the age of 18 is free to do with his life what he wishes, but it is the duty of the court to ensure so far as it can that children survive to attain that age…To take it a stage further, if the child’s welfare is threatened by a serious and imminent risk that the child will suffer grave and irreversible mental or physical harm, then once again the court when called upon has a duty to intervene.”