Two people have been arrested after police discovered three women, including a 57-year-old Irish woman, who are believed to have been imprisoned in a London home for more than 30 years.
Scotland Yard confirmed two people, in their 60s and 70s, were arrested at their home in south London this morning as part of an investigation into slavery and domestic servitude.
It followed a call to police last month from a charity on behalf of one of the alleged captives.
Police said the Freedom Charity, which aims to advise and support victims of forced marriages or honour-based violence, got in touch after they received a call following a television documentary on forced marriages.
Scotland Yard said further inquiries by police revealed the location of the house.
It said with the help of sensitive negotiations conducted by the charity, the three women - the Irish woman, a 69-year-old Malaysian woman and a 30-year-old British woman - were all rescued.
All three, who police described as "highly traumatised", were taken to a place of safety where they remain.
Detective Inspector Kevin Hyland, from the Metropolitan Police's human trafficking unit, said: "We applaud the actions of Freedom Charity and are working in partnership to support these victims who appear to have been held for over 30 years.
"We have launched an extensive investigation to establish the facts surrounding these very serious allegations.
Speaking outside Scotland Yard's headquarters in central London, Det Insp Hyland said: "We've established that all three women were held in this situation for at least 30 years. They did have some controlled freedom.
"The human trafficking unit of the Metropolitan Police deals with many cases of servitude and forced labour. We've seen some cases where people have been held for up to 10 years but we've never seen anything of this magnitude before."
The detective said there was a delay in arresting the suspects, who are both non-British, after the women were freed on 25 October, as police tried to establish the facts of the case.
"The women were released as soon as possible," he said.
"There was a delay in the arrest. This was down to the fact that we had to work very carefully with these people who were highly traumatised and it was very difficult to establish the facts.
"We needed professional assistance from outside agencies. The last thing we wanted to do was increase that trauma.
"Until we had facts to justify where we are now, we delayed that arrest."
Det Insp Hyland said he was unable to confirm any relationship between the suspects and the three women who were freed.
"A television documentary on forced marriages relating to the work of Freedom Charity was the catalyst that prompted one of the victims to call for help and led to their rescue."
Officers said the two suspects, a 67-year-old man and a 67-year-old woman, have been taken to a south London police station where they remain in custody.
Aneeta Prem, Freedom Charity founder, said the alleged victims, who are believed to have suffered physical and mental harm, were able to walk out of the property after extensive calls with the charity.
She told Sky News: "We started in-depth talks to them when they could, it had to be pre-arranged. They gave us set times when they were able to speak to us.
"It was planned that they would be able to walk out of the property. The police were on standby.
"They were able to leave the property, but it was done in such a way ... it was a very, very excellent way it happened."
Ms Prem said the two people arrested were considered the "heads of the family", and that the women were "absolutely terrified" of them.
She added: "They felt they were in massive danger.
"I don't believe the neighbours knew anything about it at all. It was just an ordinary house in an ordinary street.
"They were very restricted on everything they could do."
Asked about what help the women will be given, the charity founder said: "They are going to be afforded all the help and support that can be. I'm so grateful they saw the news.
"Now they will try to re-build their lives."