The Cambridge Five were British civil servants that worked for various departments and secret organisations between October 1935 and April 1952. They were also Soviet spies. Anthony Blunt’s career was solely for the British Security Service (MI5). Guy Burgess swapped roles and departments frequently, working for the Secret Intelligence Service (SIS), the Special Operations Executive (SOE), MI5, and lastly the Foreign Office (FO). John Cairncross also had a peripatetic career in the FO, then HM Treasury (HMT), Government Code and Cypher School (GC&CS, now known as GCHQ), SIS, and the Ministry of Supply (MoS). Donald Maclean stuck to a career in the FO choosing to rise up the ranks. Harold ‘Kim’ Philby, the most famous of the Five, details his SOE and SIS career in his autobiography.
There was a small group of civil servants in London and Washington D.C who knew of the leak investigation looking for a Russian spy inside the British Embassy in Washington DC. Philby was part of this small group.
Less than a month after arriving in Washington, Philby was taking an active role, in the investigation, as recently declassified files show:
“During our conversation this morning on the leakages of Embassy telegrams in 1945, I expressed a doubt about whether we were justified in concentrating too exclusively on members of the subordinate staff or on persons with known Communist affiliations.”
The investigation hinged on a joint UK and US effort commonly known as VENONA, which led to Maclean being identified and confirmed as the Russian spy by the Spring 1951. The FO placed Maclean under surveillance, giving him the codename CURZON, and his every London move was to be recorded and reported daily from Monday 23 April 1951 onwards.
On 16 May Philby made a critical mistake. A poorly drafted telegram led him to conclude that the surveillance was about to turn to action, with Maclean to be brought in for questioning soon after 23 May. A subsequent report noted:
“It is not true that anyone in Washington was fully in the picture about progress of the investigation and the intentions of the authorities in London.”
Thus, with those in Washington only having snippet updates from London to draw upon, it is easy to posit how incorrect conclusions were drawn. Most importantly the date for Maclean’s interview had yet to be finalised by the relevant teams in London. Therefore Washington, and Philby, could only guess when Maclean was to be interviewed. The Soviet Residency in London, thanks to Philby’s intelligence concluded that Maclean was to be interviewed on Monday 28 May, and made plans for his escape before this date.
It is now possible to piece together the events of late May 1951, thanks to the availability of declassified files. A meeting of key officials took place on the afternoon of 24 May 1951. The purpose was to discuss a paper titled: Considerations affecting the action to be taken in the case of D.D. MACLEAN. The minutes discussed how to reduce Maclean’s access to secret information:
“Sir Roger Makins explained that when he had been in a position to do so he had in fact refrained from passing to Mr. Maclean certain papers which he would normally have marked for him.”
The meeting concluded that the Foreign Secretary should be given an update on the case, and subject to his granting approval, Maclean should be interviewed between 18 and 25 June whilst Maclean’s wife was in hospital.
On the morning of Friday 25 May, Sir William Strang submitted a MI5 summary to the Foreign Secretary, including the proposal that Maclean should be interviewed by the Security Service in June. The Foreign Secretary also gave approval that the United States Security Authorities should be made aware of the MI5 summary and the date for Maclean’s interview.
The sequencing is crucial.
A previous agreement meant that MI5 were duty bound to inform the US security bodies of proposed action at an early stage. MI5 duly wrote to their representative in Washington after the Foreign Secretary’s meeting (25 May). MI5 also enclosed a copy of the paper discussed the previous day (24 May), which said:
“…anticipated programme of events up to the date at the end of June upon which MACLEAN is to be interviewed, this being at present provisionally fixed for 19.6.51.”
This information was shared with Philby, but it was too late. The defection plan he had worked out with Burgess, to get Maclean way from London was already underway, with no way to warn them that the interview date was confirmed for June, not shortly after the 23 May as Philby had interpreted. Just before midnight on the 25 May Maclean and Burgess left England for the last time.
Their defection destroyed the Cambridge Five. Before this only Maclean was suspected of being a Russian spy. The fact that Burgess went too, meant that Philby came under suspicion and was recalled to London and placed on gardening leave pending investigation. This in turn lead to investigations into Blunt and Cairncross. Less than a year after the defection all Five had ceased to be useful to Moscow just as the Cold War was really beginning.