A madam who ran a brothel empire from a flat behind Surbiton station has been sentenced to two-and-a-half-years in prison after a judge ruled she did not know she was using “sex-slaves” as prostitutes.

Nikki Chen, 57, made more than £120,000 in the nine months she was watched by police but was running brothels for years. She was given time off for pleading guilty.

Her ex-boyfriend Michael Dalton, 43, whose failed defence for being seen at four brothels run by himself and Chen was that he was an informant for the police, was sentenced to three years.

He made in excess of £50,000 the judge ruled at Croydon Crown Court on Thursday, August 5.

Both could have faced considerably longer jail terms but for a ruling by the judge that he could not be sure either had been aware the prostitutes were being held in “debt bondage” - coerced into paying up to £28,000 out of their earnings and facing threats to their families in Thailand.

During his trial Dalton, who lived in Kingston Road, Leatherhead, with Chen, and had a variety of fast cars, had told a jury: “As I became more aware of the situation and how these girls came into the country and the way they had to work off these debts I wasn't happy with the situation at all.”

But the judge said he could not be sure Dalton was referring to specific women or the debt bondage system in general.

He also ruled against a claim by prosecutors that Dalton had been seen shoving a woman toward a brothel. Defence counsel said the image of Dalton with his hand behind a woman's back crossing the road could have been “gentlemanly or charming”.

Judge Daniel Flahive said Chen's past as a prostitute had motivated her to run brothels, “exploiting others for financial gain.”

But he said: “Yesterday when I heard you give evidence I was not sure you knew you were using girls that were subject to debt bondage. On evidence it is more probable than not that during a period of time you did use such girls.”

The brothel was open for 12 hours a day, seven days a week, with women charging £60 to £100 an hour for sexual services. They would pay 10 percent to a maid and split the rest 50-50 between themselves and Chen.

Chen has already agreed to pay back £120,000 and plans to return to her home country of Taiwan when released. Dalton will face a proceeds of crime hearing later this year where police begin to claw back as much of the pair's ill-gotten gains as they can.

*Ian Garrett, 43, of Kingston Road, Epsom, also admitted conspiring to traffic women in the UK. He received an 18-month prison sentence in July at Croydon Crown Court after admitting admitting conspiracy to traffic within the UK for sexual exploitation.

Garrett was seen carrying luggage that belonged to trafficked South East Asian women when he escorted them to the brothels in Surbiton, Egham, West Drayton and Sunbury.

*Li Yen Lew, 28, from Grange Road, Chessington was charged with conspiracy to control prostitution, controlling prostitution and money laundering.