The article reviews recent developments in England in the law of necessity as a defence to crime and calls for its further extension. It argues that the defence of necessity presents the criminal law with difficult questions of competing values and the ordering of harms. English law has taken a nuanced position on the respective roles of the courts and the legislature in the ordering of harms, although the development of the law has been pragmatic rather than coherently theorised. The (...) law has granted necessity some scope as an exculpatory principle in the law of general defences, but it has also respected the primacy of the legislature as the legitimate arbiter of many of the competitions of value that necessity throws up. The recognition of necessity has not been in the form of a single unified defence of that name. Rather it has taken the form of a number of defences, based on a principle of necessity, but with different nomenclature and different rationales. This approach to necessity is defended as right in terms of principle and policy. Any further development of necessity as a general defence should be restricted to two contexts, namely those of emergencies, and of conflicts of duty, where a danger of death or serious injury is present. (shrink)