Prior to the present programme of work, the effects which a tidal power barrage would have on the region, during both construction and operation, had not been studied in detail. This volume of the Detailed Report therefore represents a significant extension of work into these aspects of the Severn Barrage Project. In the Regional Study, a number of benefits have been identified, some of which may represent net benefits nationally. The economic assessment of both regional and national benefits and costs is presented. The second part of this volume reports on the work done on the Legal Background for the Project. (author).