During the Second World War, the name MI6 was used as a flag of convenience, the name by which it is frequently known in popular culture since. In the immediate post-war years under Sir Mansfield George Smith-Cumming and throughout most of the 1920s, SIS was focused on Communism, in particular, Russian Bolshevism.

Why is SIS head called C?

Annual reports are also made to the Prime Minister. The chief of the Secret Intelligence Service typically signs letters with a "C" in green ink. This originates from the initial used by Captain Sir Mansfield Smith-Cumming, when he signed a letter "C" in green ink. Since then the chief has been known as "C".

Is MI6 Her Majesty's Secret Service?

In the shadowy world of espionage there is no spy agency more legendary than Her Majesty's Secret Service. Founded over 100 years ago, it has evolved into a global spying network. Better known by its old government identifier as MI6, the service didn't officially exist until 1994.