During the last forty years several preoccupations have driven historians to examine the work of public health authorities in Britain. Most recently it has been the effort to explain the fall in mortality during the nineteenth century. The issue has been raised in its contemporary form by the well-known works of Thomas McKeown and associates, who grant to conscious human intervention – clinical medicine, public health, or social welfare – only a small part in the mortality decline before the twentieth century. While conceding that the construction of sewage systems, the provision of protected water supplies, and vaccination for smallpox had some effect on human mortality and suggesting that spontaneous changes in the virulence of its agent accounted for the diminished mortality from scarlet fever, these authors have argued that only improvements in the standard of living, especially in nutrition, could account for the magnitude of the mortality decline. For some years historians accepted this analysis with little question, showing particular appreciation for McKeown's demonstration that clinical intervention could not possibly account for mortality decline on such a scale. But recently they have turned their attention to the most debatable part of McKeown's thesis, the role played by mass intervention by public authorities. So important has this issue become, that it dominates the discussion of public health in the new Cambridge Social History of Britain. For England and Wales some of the most interesting recent work is by Simon Szreter and Anne Hardy.