The Circus: MI5 Operations 1945-1972 (1983) By Nigel West
 
This book details the failures of British intelligence to detect the soviet spies high up in it own ranks
 
Nigel West is a pen name for Rupert Allason, who has written quite a number of books on espionage. A member of parliament from 1987-1997, he has lectured at both the CIA and, ironically, the KGB.

If you weren't an adult during the years that the Cambridge Five spy ring (active from the 1930s-1950ish) was seeping into the headlines (1950 on), this book will send you off to Wikipedia constantly (I should have realized the back cover's statement "everybody knows about Philby, Burgess, Maclean and Blunt - But what about the others?" was a warning). There is an assumption that you're familiar with the major communist agent cases discovered in British MI5 / MI6 during the 1970s and need minimal references before taking on more.
 
Hard Cover with Dust Jacket
196 pages
In Good Condition