This thesis is concerned with an analysis of British governmental attitudes and responses to communism in the United Kingdom during the early years of the Cold War, from the election of the Attlee government in July 1945 up until the election of the Wilson government in October 1964. Until recently the topic has been difficult to assess accurately, due to the scarcity of available original source material. However, as a result of multiple declassifications of both Cabinet Office and Security Service files over the past five years it is now possible to analyse the subject in greater depth and detail than had been previously feasible. The work is predominantly concerned with four key areas: firstly, why domestic communism continued to be viewed as a significant threat by successive governments – even despite both the ideology’s relatively limited popular support amongst the general public and Whitehall’s realisation that the Communist Party of Great Britain presented little by way of a direct challenge to British political stability. Secondly, how Whitehall’s understanding of the nature and severity of the threat posed by British communism developed between the late 1940s and early ‘60s, from a problem considered mainly of importance only to civil service security practices to one which directly impacted upon the conduct of educational policy and labour relations. Thirdly, how official counter-subversion methods were formulated and enacted over the period – from remarkably limited beginnings as small-scale vetting reform to a wide-ranging program of surveillance and counter-propaganda by the early 1960s. And finally, whether such responses can be judged as proportional with the benefit of historical hindsight, or if the British government’s conduct should be regarded as an egregious example of reactionary censorship and infringement of civil liberties in the modern era.