Florence Samarasinha, 41, stood to gain thousands from her husband Nimal's pension policies and the equity on their home.
She slumped forward in the dock and shouted 'No' as the jury of eight men and four women convicted her of murder and soliciting murder. She will be sentenced on 17 December.
The housing benefits official for Croydon council recruited a hitman to ambush and assassinate her husband Nimal, 37, outside their house in a quiet suburban Surrey street, the court was told.
Samarasinha, born in Nigeria, had lied her way into her pounds 30,000-a-year job by claiming she had five A-levels and a BA honours degree from Cambridge University. In fact she had no qualifications.
The court was told that Samarasinha enjoyed the trappings of power. She drove a silver Mercedes, sent her daughter to a fee-paying school, and spent pounds 100 a day on gambling.
'She frequently spent more than half the working day in amusement arcades, making false excuses to her staff to explain where she was,' David Calvert-Smith, for the prosecution, said.
When her addiction to fruit machines and bingo plunged her into debt, she turned to prostitution - charging pounds 100 a customer.
But in 1990 her 12-year marriage to the aircraft engineer broke down and divorce proceedings started involving a battle for custody of the couple's daughter, now 14.
Suspicious about her activities, Nimal Samarasinha hired a private detective to arrange an appointment with his wife through an escort agency and then video what happened.
The two-minute tape, played to the jury, shows a topless Samarasinha, dressed only in her panties, offering the detective a massage and then handing back some money when he declines sex.
In the video, she says: 'I'm new in this business this year to pay off some debts. If there is anything you want me to do, just say so.'
Two former clients, Peter Ezzard and Kevin Davey, said Samarasinha had given them hand relief and sex for pounds 100. Another customer, Joseph Donovan, told of hour-long sex sessions.
Samarasinha said she had made a deal with the madam of the escort agency to go undercover to expose housing benefit fraud.
Samarasinha realised she would lose her job and the custody of her daughter if details of her secret life were revealed. She was pounds 34,000 in debt at the time. The court was told that she asked Alex Cheetham, the head of Croydon's police consultative committee, to find her a contract killer for pounds 500. Mr Cheetham admitted that he regularly visited escort agencies and paid for sex.
She also approached others, including a call-girl, Jackie Bartlett, asking if they knew anyone who could kill her husband. One of those, Simon Wash, was offered a council contract for his cleaning firm if he could arrange the murder.
Nimal, who worked for Bristow's Helicopters in Redhill, Surrey, was knifed to death in January last year outside the couple's home in Wallington. Police are still seeking the killer, whose identity remains a mystery.
Mr Calvert-Smith said: 'The circumstances of the killing prove it was an assassination. She is a strong-willed and manipulative person, prepared to say and do anything to achieve her own ends.'
He added that Samarasinha gave 'every appearance of respectability and responsibility' while in her high-powered post.
Samarasinha denied having anything to do with the murder - or approaching anyone to kill her husband.
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