This chapter traces the steps taken to implement the Stewart Report, and the fresh mandate for the Security Service which it produced. This was the Attlee Directive, a bowdlerized version of which adopted in 1952 became known as the Maxwell Fyfe Directive, diluting the political supervision of the Service which the Attlee Directive had embraced. The Attlee Directive was never published and was released to the National Archives in 2009, while the Maxwell Fyfe Directive was revealed only in 1963. What has not been revealed until now, however, is the expansion of MI5’s mandate by means of secret Supplementary Directives, in response to the clear failure of MI5 to operate within the boundaries of its authority.