Medical malpractice may be defined, broadly, as any unjustified act or failure to act upon the part of a doctor or other health care worker which results in harm to the patient. This chapter considers the means, under the civil law, by which a victim of such malpractice may pursue a claim for redress, and the difficulties that lie in his way. The patient must establish that the defendant, who may be a doctor, nurse, National Health Service trust, or a health authority, owed him a legal duty of care. In relation to general practitioners, who operate outside hospitals, these clearly owe a duty of care to their own patients, that is, those who are registered with them. Analytically, causation subdivides into two main stages: it must be shown that the defendant's breach of duty was a factual cause of the claimant's harm; and if so, the law must then also deem it to be the legal cause.