INTRODUCTION

In the first volume of The Guy Liddell Diaries the author was preoccupied with internment, German espionage and the threat of German infiltration in Ireland. He was also concerned with the development of the double-cross system and its management through a new branch of the Security Service created during a disastrous period of reorganisation. In this second volume, the threat of imminent invasion of Britain has been lifted and MI5 is on the offensive, exploiting intercepted German wireless traffic to interdict enemy spies, but nevertheless there remains a continuous demarcation wrangle between SIS’s Section V and B Division over the proper supervision of that most secret of sources, ISOS.