must be good as @Mad Al 's books will take some beating
"For over 100 years, the agents of MI5 have defended Britain against enemy subversion. Their work has remained shrouded in secrecy - until now.
This first-ever authorized account reveals the British Security Service as never before: its inner workings, its clandestine operations, its failures and its triumphs."
Given how long it is I nearly didn't bother but I'm glad I did, one of the most interesting books I've read in years.