The woman pictured has been named as Josephine Herival, according to ITV News.
She was featured in a 1997 documentary on the death of Maoist Sian Davies (44), who died after falling from a window.
Miss Davies died after plunging from the bathroom of a house rented by the couple suspected of holding three women against their will.
Aravindan Balakrishnan and his wife Chanda were arrested last week by UK police amid allegations that they held three women for more than 30 years.
The 'slave' case of three women, including a 57-year-old Irish woman, came to light after the Irishwoman rang the Freedom Charity last month to say she had been held against her will.
Scotland Yard said that part of the agreement on October 25 when the women were removed from the address was that police would not take any action at that stage.
None of the women was reported missing after being rescued, police said, and all three are now in the care of a specialist non-governmental organisation.
Officers have recovered a birth certificate for the 30-year-old woman, who is believed to have lived her entire life in servitude, but no other official documents for her have been found.
The couple, who are of Indian and Tanzanian origin and came to the UK in the 1960s, have now been released on bail until a date in January.
A Lambeth Council spokeswoman said the case was "very complex" dating back decades and was a police-led operation, adding: "We are working very closely with police."