A man who authorities believe brainwashed and enslaved three women for three decades met two of his victims through a "shared political ideology", claim police.
Police say a couple, both 67, arrested for questioning in relation to the enslavement of three women are from Tanzania and India, and migrated to the UK in the early 1960s.
Officers believe they met the older victims, a 57-year-old from Ireland and a 69-year-old from Malaysia, through shared beliefs.
The couple have been bailed, pending further inquiries.
In a statement, Commander Steve Rodhouse of the Metropolitan Police, said: "We believe that two of the victims met the male suspect in London through a shared political ideology, and that they lived together at an address that you could effectively call a 'collective'.
"Somehow that collective came to an end and the women ended up continuing to live with the suspects.
"How this resulted in the women living in this way for over 30 years is what are seeking to establish, but we believe emotional and physical abuse has been a feature of all the victims' lives."
Police have been conducting inquiries around Peckford Place, Lambeth.
The women were freed after one called the Freedom Charity asking for help.
They are currently being cared for by a specialist non-government organisation, and Commander Rodhouse said they were in an "emotionally fragile and highly vulnerable" state.
Aneeta Prem, founder of the Freedom Charity, told BBC News the three women are "quite stressed about the amount of detail that is being revealed".
She said they were "very concerned about the media attention" and they are worried that they will be found.
Prem said: "These women have had traumatic and disturbing experiences, which they have revealed to us.
"What needs to happen now is that the three victims, who have begun a long process of recovery, are able to go through their rehabilitation undisturbed, without being identified."
Police have said the two main suspects were previously arrested in the 1970s, but have not revealed why.
Officers said the women lived in such fear that they only agreed to leave the property in which they were allegedly being held on condition that police agreed not to arrest the couple.
"Part of the agreement on 25 October when they were removed from the suspects' address was that police would not at that stage take any action. Since that date we have been working to gain their trust and evidence: that came to fruition on 21 November when we were in a position to make arrests," said Commander Rodhouse.
The 30-year-old is believed to be the daughter of the captor and the 57-year-old Irish woman who rang for help, reports the Observer.
The MP for the area, Tessa Jowell, said she had been briefed by the Met. "I don't think it is a fair representation to call it a cult. Cult-like perhaps, but what will come out over the next few weeks is the sheer complexity of this situation," she told the Observer. "This was a bizarre household, a unique and very unusual story, but the coercion and fear is no different from that of so many vulnerable women who can't leave abusive relationships because of fear, dependency and terrible abuse that becomes normalised."