Those freed on Oct. 25 are a 69-year-old Malaysian woman, a 57-year-old Irish woman and a 30-year-old British woman, police said.
Kevin Hyland, head of the Metropolitan Police's human trafficking unit, said the women are "highly traumatized" having had "no real exposure to the outside world" for the past 30 years.
"Trying to find out exactly what has happened over three decades will understandably take some time," he said.
Police initially said they did not believe any of the victims were related. Later, however, they appeared to backtrack, saying the relationship between the three women is part of the investigation and they will not speculate on it.
The force also said there is no evidence to suggest anything of a sexual nature — but cautioned that the investigation is still not finished. Police would not speculate on any motivation, name the suspects' nationalities or say if the suspects were a couple.
The revelations raised numerous questions — all still unanswered — about how the women's ordeal began and why it endured for so long. What brought them to London? What freedoms — if any — did they have? What restrictions and conditions were they subject to? Did neighbors ever see them, or did they ever try to escape?
The women — whose names have not been released — are now safe at an undisclosed location in Britain and have been working with severe trauma experts since their rescue, Hyland said.
It is not known how the women ended up in the house. The 30-year-old, who would have had to either been born in the home or enter it as an infant given the police timeline, appears to have been held in domestic servitude for her entire life, police said.
The Irish woman called the charity from what appears to be an "ordinary house in an ordinary street," said Aneeta Prem, founder of the charity that promotes awareness of child abuse, forced marriages and honor killings.
Police said the woman "found the courage to call" in October after seeing a documentary on the BBC about forced marriages. What followed were secret, "in-depth" conversations with the women, Prem told Sky News.
"It had to be pre-arranged when they were able to make calls to us and it had to be done very secretly, because they felt they were in massive danger," she said.
Her charity first sounded the alarm to Metropolitan Police's sexual offenses exploitation and child abuse unit; the case then was passed on to its human trafficking unit.
By tracking where the woman's calls were coming from, London police managed to find the house in the borough of Lambeth, south of the River Thames. London police were keeping the exact location of the house secret.
After repeated, tentative calls to the charity, two of the captive women agreed to meet at another location on Oct. 25, police said. The first two — the British woman and the Irish woman — walked out under their own power and identified the house where they'd been held. At that point, police said they went in and rescued the 69-year-old Malaysian woman.
Hyland said there was a delay in arresting the two suspects — neither of whom are British — as police worked to establish the facts of the case and to ensure that the women who had escaped were not further traumatized. The suspects are now in custody at a south London police station.