Stephen De Mowbray joined MI6 and in 1960 he was sent to Washington as liaison officer to the CIA. In 1961 he became involved in the Anatoli Golitsyn case. In March 1962 he arranged for Arthur Martin, head of MI5's D1 Section, to interview Golitsyn. Golitsyn claimed that Kim Philby, Donald Maclean and Guy Burgess were members of a Ring of Five agents based in Britain. He also provided material that helped to establish the guilt of George Blake and John Vassall. Other information suggested that Alister Watson was a spy. However, Golitsyn was unable to provide any new evidence that would be acceptable in a court of law. (1)
Ever since Guy Burgess and Donald Maclean fled to Moscow, Kim Philby was suspected of being a Soviet agent. An old friend of Philby's, Flora Solomon, disapproved of what she considered were Philby's pro-Arab articles in The Observer. It has been argued that "her love for Israel proved greater than her old socialist loyalties." (2) In August 1962, during a reception at the Weizmann Institute, she told Victor Rothschild, who had worked with MI6 during the Second World War and enjoyed close connections with Mossad, the Israeli intelligence service: "How is it that The Observer uses a man like Kim? Don't the know he's a Communist?" She then went on to tell Rothschild that she suspected that Philby and his friend, Tomas Harris, had been Soviet agents since the 1930s. "Those two were so close as to give me an intuitive feeling that Harris was more than a friend."
It was expected that Arthur Martin would be sent out to interview Kim Philby in Beirut at the beginning of 1963. However, it was decided to send Philby's friend and former SIS colleague Nicholas Elliott instead. According to Philby's later version of events given to the KGB after he escaped to Moscow, Elliott told him: "You stopped working for them (the Russians) in 1949, I'm absolutely certain of that... I can understand people who worked for the Soviet Union, say before or during the war. But by 1949 a man of your intellect and your spirit had to see that all the rumours about Stalin's monstrous behaviour were not rumours, they were the truth... You decided to break with the USSR... Therefore I can give you my word and that of Dick White that you will get full immunity, you will be pardoned, but only if you tell it yourself. We need your collaboration, your help." (3)
Roger Hollis wrote to J. Edgar Hoover on 18th January 1963, about Elliott's discussions with Kim Philby: "In our judgment Philby's statement of the association with the RIS is substantially true. It accords with all the available evidence in our possession and we have no evidence pointing to a continuation of his activities on behalf of the RIS after 1946, save in the isolated instance of Maclean. If this is so, it follows that damage to United States interests will have been confined to the period of the Second World War." (4) This statement was undermined by the decision of Philby to flee to the Soviet Union a week later.
It later emerged that Philby met Yuri Modin in Beirut just before he defected. Modin had been the KGB controller for Blunt, Philby, Burgess and Maclean. Modin later wrote: "To my mind the whole business was politically engineered. The British government had nothing to gain by prosecuting Philby. A major trial, to the inevitable accompaniment of spectacular revelation and scandal, would have shaken the British establishment to its foundations... the secret service had actively encouraged him to slip away... spiriting Philby out of Lebanon was child's play." (5)
Arthur Martin, head of the Soviet counter-espionage section, and Peter Wright spent a great deal listening to the confession that Kim Philby had made to Nicholas Elliott. Wright later argued: "There was no doubt in anyone's mind, listening to the tape, that Philby arrived at the safe house well prepared for Elliott's confrontation. Elliott told him there was new evidence, that he was now convinced of his guilt, and Philby, who had denied everything time and again for a decade, swiftly admitted spying since 1934. He never once asked what the new evidence was." Both men came to the conclusion that Philby had not asked about the new evidence as he had already been told about it. This convinced them that the "Russians still had access to a source inside British Intelligence who was monitoring the progress of the Philby case. Only a handful of officers had such access, chief among them being Hollis and Mitchell." (6)
Plans for Philby's interrogation were known to five members of the Service, of whom only Roger Hollis and Graham Mitchell had long enough service and good enough access to classified information to fit the profile of a long-term penetration agent. Hollis and Martin asked MI6 for help. Stephen De Mowbray was assigned to the task: "There were extraordinary things going on... Martin was running people against the Soviets and those operations were going wonky.... Meanwhile Peter Wright's bugging devices, which had been installed in Soviet premises around the world, were also failing to produce intelligence ... I was utterly horrified at the thought that this was happening." (7) The author of Spycatcher (1987) says that Mowbray was appalled by Hollis' decision (to close down the investigation), and immediately took it to be a crude attempt at in-house suppression, the very thing MI5 accused MI6 of with the Philby affair." (8)
In 1964, De Mowbray was posted to Washington where he worked more closely with Anatoli Golitsyn and his sponsor in the CIA, James Jesus Angleton. It has been argued that Golitsyn became an increasing "liability" because of his "passionately paranoid tendencies". "De Mowbray disagrees with the portrayal of Golitsyn. He says he has been misrepresented and disputes details presented of Golitsyn's visits to the UK, arguing that some of them were genuinely productive in terms of intelligence leads." (9)
In 1979 Stephen De Mowbray left MI6 as he believed officials had failed to take seriously the claim that British intelligence had been further penetrated by the KGB. "I could not reconcile myself to doing nothing: I had made so many commitments to myself and to others to pursue the problem to the end that I could not wash my hands and forget about it... It was a very difficult situation for years on end."
For 30 years Stephen De Mowbray has maintained a self-imposed silence on a career that once took him to the heart of one of British intelligence's most controversial episodes.
In 1979 he quit his job with the Secret Service because he believed officials had failed to take seriously the claim that British intelligence had been further penetrated by its enemy - the Soviet Union's KGB.
A number of spies had been discovered in the 1960s but De Mowbray believed there were more. But he found no-one at the top willing to listen...
When the small group added in Golitsyn's claims they came to believe that there was a mole at the very top - either Graham Mitchell, the number two at MI5, or his boss Roger Hollis.
"I vowed to myself that I would never let go of this case," recalls De Mowbray.
In his authorised history of MI5, Christopher Andrew describes the investigations into Hollis and Mitchell as "the most traumatic episodes in the Cold War history of the Security Service".
Mitchell was investigated first. As recounted in the authorised history, this involved bugging his phone, feeding him false information and putting him under close surveillance.
"We followed Mitchell all over the place, downtown when he left from the office, trying to chase him up the steps in Waterloo when he went home," recalls De Mowbray.
(1) John Costello, Mask of Treachery (1988) page 583
(2) Flora Solomon, Baku to Baker Street (1984) page 226
(3) Genrikh Borovik, The Philby Files: The Secret Life of the Master Spy - KGB Archives Revealed (1995) pages 344-345
(4) Roger Hollis, letter to J. Edgar Hoover (18th January 1963)
(5) Yuri Modin, My Five Cambridge Friends (1995) page 236
(6) Peter Wright, Spycatcher (1987) pages 170
(7) Gordon Corera, BBC News (26th January 2010)
(8) Peter Wright, Spycatcher (1987) page 202
(9) Gordon Corera, BBC News (26th January 2010)