The authorized history of the world's oldest foreign intelligence service, drawing on hitherto secret documents. Britain's Secret Intelligence Service (MI6) was born a century ago amid fears of the rising power of other countries, especially Germany. The next 40 years saw MI6 taking an increasingly important & largely hidden role in shaping history. This revelatory account draws on a wealth of archival materials never before seen by outsiders to unveil the inner workings of the world's 1st spy agency. MI6's early days were haphazard but it was quickly forged into an effective organization during WWI. During the war years, MI6 also formed ties with the USA—harbingers of a relationship that would become vital to both. These early years also saw the development of techniques that would become plot devices in books & films—forgery, invisible ink, disguises, concealing mechanisms etc. The interwar years were nominally peaceful, but Britain perceived numerous threats, all of which MI6 was expected to keep tabs on. The outbreak of WWII again caught MI6 off balance, & high-profile blunders (& the memoirs of MI6 operatives like Graham Greene) created an impression of ineffectiveness. At the same time the service was pioneering cryptography at Bletchley Park, breaking the Enigma code & devising the methods & equipment inspiring Ian Fleming's novels. The aftermath of WWII was as dramatic as the war itself had been, because 1945-49 saw not only the end of the British Empire but also the emergence of a new sort of conflict—the Cold War. We witness MI6 wrestling with these epic changes as it tightens its bonds with the newly christened CIA, changes that would dictate the shape of the service & the world for decades.