This is a fascinating book written with great verve and aplomb. The history of the Secret Intelligence Service - MI6 as it is familiarly known today - has been charted by many, but few have possessed Corera's narrative style. Particularly enthralling are the sections about the 1950s and early 1960s, when Soviet moles seemed to be emerging with regularity and the KGB appeared all too often to be winning the intelligence war. But the story of perhaps MI6's greatest success from that era - that of the defector Oleg Penkovsky - is the most compelling of all, with Corera recreating with real authenticity the tense, taut discussion (interrogation) between MI6 (and the CIA) and Penkovsky in Room 360 of London's Mount Royal Hotel.