MI5 spies were regularly summoned to 10 Downing Street for clandestine meetings with Labour prime minister Harold Wilson to share material on striking seamen, hitherto top secret files from 1966 reveal.
The full extent of his close relationship with senior MI5 officers is contained in scores of documents declassified on Tuesday at the National Archives in Kew.
They also show how MI5 blacklisted a Labour MP who Wilson agreed should not be appointed Solicitor General despite being a distinguished human rights lawyer posing no danger to national security.
The files shed particular light on Wilson’s hostility towards a strike by the National Union of Seamen (NUS, now part of the RMT), whose members demanded a 40-hour week.
It emerges that the Security Service ran informants inside the NUS and conducted phone taps on its members.
There is no evidence of any objection from Wilson who – despite his left-wing credentials – harboured deep suspicion of the Communist Party (CP).
In one previously highly classified file, many of which are partly redacted, MI5 chief Sir Martin Furnival-Jones described how “the prime minister spoke to me in warm terms of the quality and value” of the agency’s intelligence.
In almost daily reports from June 1966 – at the height of the protracted strike – Richard Thistlethwaite, MI5’s go-between with Downing Street, exaggerated the role of communists.
He commented that Wilson “was clear that the Communist Party was again in the centre of the picture and that we should therefore be in a position to obtain more information”.
The MI5 reports name Bert Ramelson, the CP’s industrial organiser, and NUS strikers described as “quite open Communists” including Jack Dash, Jack Coward, and Gordon Norris.

‘Numerically weak’
As intelligence was described as “coming in thick and fast”, MI5 officers expressed concern that they should “prepare something” for a meeting with Wilson and Edward Heath, leader of the Tory opposition, “which would not imperil our sources”.
It became clear that Wilson was referring to CP members in what became his notorious reference to “a tightly knit group of politically-motivated men”.
However, the MI5 files say that while CP members had been influential in some local strike committees, they were “numerically weak” in the NUS and their role was diminishing.
Perversely, that caused concern to MI5. On 17 June 1966, Furnival-Jones reported that “as the [Communist] party looked as though it was going to withdraw from the strike, our sources of information would dry up”.
MI5 officers noted that the CP had “reached the conclusion that its efforts to extend the strike…through the other unions, notably the TGWU (Transport Workers’ Union, now Unite), had failed”.
The files show that MI5 was strongly opposed to a threatened government inquiry into the dispute.
The agency was worried that an inquiry would expose how it received information, described in the files as “an amalgam of human sources and eavesdropping devices”.
One unnamed MI5 officer was worried that an inquiry might also provoke an “incipient McCarthyism in this country”.
The seamen’s strike was settled in early July 1966. The NUS and the National Union of Railwaymen merged in 1990 to form the RMT (National Union of Rail, Maritime, and Transport Workers).
‘Mighty thin’
MI5 targeting of trade union leaders continued throughout the Cold War, the newly released files confirm.
These include a report to Sir Burke Trend, the cabinet secretary, saying that Wilson agreed that Barbara Castle, his Labour and subsequently Employment Secretary, “should be kept informed of all relevant covert intelligence about industrial disputes”.
MI5 warned that the matter was “very sensitive in terms of its nature and its sources”.
In her diaries published many years later Castle recorded that one of her early discoveries was that “the Minister of Labour has always been furnished with security reports on the Trade Unions”.
She added: “The more I read these reports the less confidence I have in our intelligence. To begin with the material is always mighty thin and most of it would be obvious anyway to an informed politician”.
MI5 accumulated many files on trade union leaders, including Hugh, later Lord, Scanlon, of AUEW, the electricians’ union and Jack Jones, of the TGWU, despite their support for Labour’s pay policy and opposition to their left wing.
MI5 was particularly active during the 1984/85 miners’ strike, bugging both Arthur Scargill, the NUM president, and Mick McGahey, the union’s vice-president and lifelong communist.
Stella Rimington who was to head MI5, later justifying spying on the NUM leadership on the grounds that Margaret Thatcher regarded it as “the enemy within”.
She said: “If the strike is led by people who say they are trying to bring down the government, our role [is] to assess [them]”.
She denied that MI5 itself ran agents in the NUM, but added: “That’s not to say the police or police Special Branch…might have been doing some of those things.”
A senior Home Office civil servant reported that Thatcher was “convinced that a secret communist cell around Scargill was orchestrating the strike in order to bring down the country”.
‘Valuable intelligence asset’
Others on whom MI5 kept files, the newly-released documents confirm, included members of the Campaign for Nuclear Disarmament (CND).
One document refers to CND and its “Spies for Peace” campaign. Its “primary objective”, MI5 noted, was “to acquire and publish information thought to show the State in an unfavourable light”.
The newly-released documents include a file on Niall MacDermot, a human rights lawyer who Wilson suggested should be appointed Solicitor General, a post for which he had impeccable credentials.
MI5 objected because his wife, Ludmila Benvenuto, who had been a member of a wartime Italian resistance group, had spent some years of her youth in the Soviet Union.
“The wife of a Minister would be regarded as a valuable intelligence asset” by the KGB, MI5 warned.
In a letter to this reporter in 1988, MacDermot confirmed that his promotion was blocked on the advice of MI5 on the grounds that his wife was a security risk.
He told me: “She was never a member of the Italian or any other Communist Party.
“During the war, she worked in an underground movement in Italy helping allied prisoners of war to escape, including Russian prisoners.
“There were people of all political views, except fascists, in this organisation”.