by travelling to Denmark and Sweden in 1929, where he had a chance meeting with Sophus Müller. On his return to Britain he began a systematic examination of Mesolithic stone tool collections that were held in both museums and private collections across the country, listing these many artefacts within a database. From this he was able to map the distribution of such Mesolithic tool assemblages across the island. On the basis of this research he wrote The Mesolithic Age in Britain, which was published to critical acclaim by Cambridge University Press in 1932. The book took a conservative approach to the subject by being heavily artefact-focused, although reflected Clark's growing interest in ecology and the role of Mesolithic society in adapting to climate change by discussing the technique of pollen analysis—which had recently been developed in Scandinavia—as a means of understanding ancient changes in the vegetation. Influenced by Childe, the book was rooted in the theoretical perspective of culture-historical archaeology, presenting different styles of Mesolithic tool as representations of different 'cultures', which in turn represented different peoples. The Mesolithic Age in Britain formed the core of Clark's completed thesis, which was titled "The Mesolithic, Neolithic, and Early Metal Age Industries in Britain" and submitted in January 1934. After passing his oral exam, which was conducted by Thomas Kendrick at the British Museum in London, Clark was awarded his PhD in 1934. While conducting his research, he published a number of research articles in scholarly journals such as Antiquity. In 1932, he co-founded the Fenland Research Committee with the botanists Harry and Margaret Godwin; it represented a loose association of specialists in different academic fields who all had an interest in the East Anglian Fenlands. Clark served as the group's honorary secretary, and under him all of the Committee's research projects would be promptly written up and published. The group excavated at Plantation Farm near Shippea Hill, helping to establish a basic stratigraphic chronology of the Fenland's development. In 1934 they then carried out a second excavation at Peacock's Farm, which was very important for demonstrating the advantages of interdisciplinary research and for placing British prehistory within an environmental framework. In February 1932, Clark was elected to the council of the Prehistoric Society of East Anglia, and in May 1933 became acting editor of the society's Proceedings at Childe's recommendation. In February 1934 he was made a permanent council member and