Colonel Valentine Patrick Terrell Vivian CMG CBE (1886–1969) was the vice-chief of the SIS or MI6 and the first head of its counterespionage unit, Section V. Vivian, while he was attempting to introduce new blood into the service, selected Kim Philby, who later became notorious as "The Third Man" double agent and defected to the Russians, causing considerable harm to the system he had infiltrated.