London slaves: Suspects ran a Maoist collective in the 1970s

Two suspects in an alleged case of modern-day slavery in a London suburb reportedly ran a Maoist collective in the 1970s.

The pair, who are from India and Tanzania, arrived in the United Kingdom in the 1960s and were members of political groups known to police, NBC News reports.

The man and wife, both in their late 60s, allegedly kept three women as slaves for up to 30 years, subjecting them to emotional and possibly physical abuse.

The couple were known to police for their leftist revolutionary activities. They were based in Brixton, south London, and helped recruit women for "revolutionary work." Both had served prison time in the late 1970s for assaulting a police officer.

The two were arrested last week.

A Malaysian woman, 69, an Irish woman, 57, and British woman, 30, were rescued by police last month after one of the women phoned a charity and described their situation.

In an exclusive report in the Daily Mail newspaper, the 30-year-old apparently had been writing love letters to a neighbor about her capitivity, saying that she was "trapped like a fly in a spider's web."

She wrote: "They imprisoned me here, locking all the doors and windows. I can't get out on my own, the place is crawling with them."

Letters were sent over the years to her upstairs neighbor, but there is no word on why he did not contact police.

Police are investigating exactly how the couple ensured that the women would not escape, calling their imprisonment one of "invisible handcuffs."