One of the characters is referred to as "Control". Also known by the letter C, Control is the head of British foreign intelligence, MI6. The "C" originated with the first person in charge, Captain Sir Mansfield Smith-Cumming R.N. (Royal Navy), who would sign documents with his initial and in green ink. The character "M" in the James Bond movies is a play on this, originally based on the name "Mansfield". As a matter of tradition, the succeeding directors of MI6 have continued to sign documents with the letter C (for Control), and in green ink.