The Portland Circle was a Soviet success that the British still remember.

Harry Houghton and Ethel Gee, photographed in 1970 after their release from prison.
Most readers know about the Cambridge Five, but few know about the Portland Five.
The Portland Spy Ring "could have been stopped"
four years earlier"
Declassified documents show that the infamous Soviet spy ring that leaked Admiralty documents (the British Navy Ministry until 1964 – P.G.), including information about Britain's first nuclear submarine, could have been stopped four years earlier.
In 1961, the authorities uncovered the Portland Spy Ring, named after the naval base in Dorset (on the Isle of Portland in the English Channel – P.G.) from which secrets were stolen, arresting and ultimately convicting five Soviet agents (two of whom were the British subjects we are considering (see below), two were US citizens (L.V. Cohen and M.G. Cohen) and an illegal Soviet intelligence officer, K.T. Molody, who operated under the pseudonym Gordon Lonsdale – P.G.).

The Coens

K.T. Molody
The two spies, Harry Houghton and his secret mistress, Ethel Gee, were British. Both worked at the base. MI5 documents recently handed over to the National Archives reveal that Houghton's then-wife contacted the Admiralty three times in 1955 with suspicions about her husband.
An Admiralty letter to the security services in 1956 stated that she "alleged that her husband was divulging classified information to people who should not have it." However, it added: "It is possible that all these accusations are nothing more than the outpourings of a jealous and disgruntled wife."
In March 1961, Martin Furnivell Jones, who became Director General of MI5 four years later, wrote:

M.-F. Jones
Documents document that Houghton beat his wife (they separated in 1955 and later divorced) and even attempted to kill her by pushing her off a cliff, but was stopped by passersby. When they returned home after the incident, she said he splashed gin in her face and said, "I need to get rid of you; you know too much."
Among the other allegations made in the documents were that her husband had documents marked "top secret" relating to "underwater detection equipment and torpedoes," that he returned from trips to London with wads of banknotes, that he showed her a piece of chalk which he said he used to make marks where money had been left, that he brought Poles to their apartment while refusing to reveal their names, and that he told her how he used a folded newspaper as an "identification mark."
Documents released [previously] show that after the [spy] ring was exposed, Houghton's ex-wife's communications with the press caused concern to the Admiralty and MI5.
In 1961, 56-year-old Houghton and 47-year-old Gee were each sentenced to 15 years in prison, but were released in 1970 and married the following year.
Gee always maintained that she acted solely out of love. Letters she sent to Houghton, contained in newly released documents, reveal her affection for him.
"Bunty," as she signed her letters, began each one with the words "My dear Harry," and in November 1962 she wrote that "the short time I spent with you was the happiest time of my life."
In a 1962 letter, she scolded Houghton for his "lack of courage" and two years later rejected his offer to cooperate with the authorities, saying, "Under no circumstances will I make any deal with them."
When authorities arranged for Houghton to visit her while they were both in prison, the transcript revealed that Gee, who maintained her innocence, nonetheless warned him, "Don't talk to them under any circumstances. I'd go back and do another stint."
The Guardian, September 24, 2019
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