This review was initiated in 1965 by the Nature Conservancy, then a component body of the Natural Environment Research Council but since 1973 it became an independent statutory Council. It was published on behalf of both Councils in 1976. 

Even when they were published, the site accounts were 'dated' in that the records of occurrence and abundance of some species, vegetational features, and habitat conditions, refered  to a particular point in time.  Statements about many of the rarer species are based on pre-1976 records, which in some instances were many years old.  It was well understood during the review process that  the selection of key sites is inevitably a continuing process, and that the published list was open to revision in the light ofsubsequent events.   In particular, the point was made that 'it may not be possible for all sites identified in the Review to be safeguarded'.   For this reason, and the feeling that the limitations on the scope of the review should, in time, be resolved; the concepts and methodology used would develop as scientific knowledge advances; and there would be a continuing growth in professional and public concern about the environment, it was felt that the carrying out of periodic assessments of this kind would be an essential base for the nation's policies for nature conservation.  Unfortunately this has not happened.  However, the review stands not only as an historical record but its principles still form the scientific basis for the evaluation of the site features of a management plan.  The rationale of classifying sites according to their value still echoes through conferences and policies as a reminder of the scientific rigour that permeated the early days of British nature conservation.  In these respects it is an important base line, and the introductory chapters covering its origins, rationale and methodology should be read widely by all site managers.

The following account of the review and its contents have been taken from the preface and introduction.

Volume 1 of A Nature Conservation Review provides an outline description of the wildlife resource of Britain, in terms of the wild plants and animals, in relation to their habitats and ecological requirements. The distribution and abundance of the vascular plants, vertebrates and certain groups of invertebrates are considered, but plant communities are regarded as the most useful biological basis for the characterisation of sites. The key site concept of nature conservation is discussed and a rationale given for the selection of the most important wildlife areas within the total range of variation, grouped into the major formations of coastlands; woodlands; lowland grasslands, heaths and scrub; open waters; peatlands; and upland grasslands and heaths. The actual choice of key sites is summarised in a geographical account for each formation.

Volume 2 gives a detailed account of the important biological and environmental features of each site, insofar as these were known, and with emphasis on vegetation. These site accounts are not wholly meaningful without reference to Volume i, since they assume a knowledge of certain definitions, base- line criteria, concepts, qualifications, sources and other background information presented there.

The site accounts aimed to give a concise description of the principal features by which the nature conservation value of the site was assessed. They thus tend to be comparative between sites of similar type within any formation, which may lead to different stress - and sometimes perhaps apparent inconsistency of treatment - when descriptions of dissimilar sites are compared. For instance, a species rare in one district may receive special mention, but may not be mentioned at all in places where it is common, unless it there becomes a community dominant. Moreover, different formations may require different treatment, e.g. peatland sites tend to be less extensive and diverse than upland grassland and heath complexes, so that botanical descriptions for the former are generally more detailed than for the latter. To give a full and standardised account of each site has been impossible in the present often incomplete or highly fragmentary state of knowledge, and the natural tendency has been to highlight known features of special interest. For many sites it is highly probable that further survey will disclose many other interesting features to which attention should be drawn.

A standardised format was thus rejected for, although this achieves greater consistency of treatment, it is wasteful of space and not necessarily a significant improvement when survey knowledge is incomplete. It tends, moreover, to give rather arid reading, and does not lend itself to economical emphasis of special features.

The site accounts are largely, and in many instances exclusively, botanical, for zoological knowledge is in general even more incomplete and haphazard. The presence of the more common vertebrates can usually be inferred by noting the habitat/vegetation of a site and referring to the ecological accounts of animal distribution under each formation in Vol. i. With birds in particular, it has often been necessary to omit mention of rare or even local species because of the risks of drawing unwelcome attention to their presence. For instance, many upland sites with cliffs contain nesting places of the peregrine and (in Scotland) golden eagle, but it was judged wiser not to say which ones. Where there is a risk of the collection of rare plants and invertebrates, mention of these has also been omitted, unless the occurrence is already well known or the area so large that discovery is difficult.   Knowledge of invertebrates is often scanty or totally lacking, and the mention of these is confined to sites which have been well studied, or to presence of interesting species which chance to be known in the most familiar groups of insect.

Knowledge of fungi is usually totally lacking, but the algal floras of some fresh waters are well known and receive due mention. Bryophytes and lichens are adequately surveyed for many sites (the latter especially as a result of the assiduous field work of Francis Rose and his colleagues), but lack of space often precluded mention of all except especially interesting species and communities.