Sir Roger Hollis (1905 - 1973) journalist, and head of MI5.
After a pre-war career in journalism, Hollis joined MI5 during World War II and rose quickly through the ranks, replacing Sir Dick White in 1956 as head of MI5 until his retirement in 1972. After Kim Philby's flight to Moscow in 1962 rumours began to circulate that Hollis had alerted him to his impending arrest. He was also criticised for not alerting John Profumo to the fact that he may be involved with a Soviet spy ring through his friendship with Stephen Ward and affair with Christine Keeler.
During the 60's and 70's, another spy in MI5, Peter Wright, along with Arthur Martin and another, became convinced that either Hollis or his deputy, Graham Mitchell , was a double agent, and went to see Dick White , of MI6. Amazingly, White contacted Hollis and told him to keep Mitchell under surveillance. After two years, Hollis ordered the surveillance to end, much to the fury of Wright and the Martin, but White responded by sacking Martin. Wright was unable to convince anyone else in MI5 or MI6 that he was right about Hollis. Wright retired, and wrote an account of his work at MI5. Despite attempts by Margaret Thatcher and her government to suppress the publication and distribution of the book, Spycatcher, it was finally was published in 1987. In the book Wright claimed that Hollis had been a Soviet double-agent and had been the fifth man
In her 2001 autobiography, Keeler alleged, without supporting evidence, that Hollis and Ward were part of a spy ring with Sir Anthony Blunt. He has also been accused by Arthur Martin (head of MI5's Soviet counter-intelligence section at the time), and Chapman Pincher (investigative journalist who produced several exposés of failures in British counter-intelligence) of being the 'fifth man' in the Cambridge Five spy ring.
Correction: Arthur Martin was not sacked by Dick White, he was sacked by Roger Hollis himself.
At the time of his termination, Arthur Martin was in the employ of MI5, which was Roger Hollis's bailiwick - Dick White was head of MI6 at the time.
Moreover, after his termination from MI5, Dick White himself brought Arthur Martin into MI6 where he worked until retirement.
Source: Peter Wright's 'Spycatcher'.
