In 1909, Commander, later Captain, Sir Mansfield Cumming became the first head of the Foreign Section of the British Secret Service Bureau, responsible for gathering intelligence overseas.

By 1922 Cumming's section had become a separate Service with the title SIS, commonly known as MI6. Cumming signed himself 'C'. The tradition of the Service is that all Chiefs are known as ‘C’ and sign their documents using green ink.