A British couple who were falsely accused of shoplifting in Bangkok airport and were forced to pay £8,000 in bribes to secure their release are to take legal action for compensation.

They were the victims of an extortion racket that has ensnared other foreign travellers at the airport, which handles most of the 800,000 British visitors to Thailand every year.

Stephen Ingram, 49, and Xi Lin, 45, both technology professionals from Cambridge, were detained by security guards as they went to board Qantas flight QF1 to London on the night of Saturday, April 25.

They were accused of taking a Givenchy wallet worth £121 from a King Power duty-free shop and were handed over to the police. An official release order from the local Thai prosecutor’s office subsequently conceded there was no evidence against them.

They were freed five days later after a frightening ordeal in which they said they were threatened and held against their will at a cheap motel on the airport perimeter until they had handed over the money.

The bribes were paid to an intermediary named Sunil “Tony” Rathnayaka, a Sri Lankan national in his fifties who works as a “volunteer” interpreter for Thailand’s tourist police (motto: “To serve and to protect”).

“Our main motivation is to protect other innocent British tourists from being caught up in this nightmare,” said Ingram last week. “We intend to take every legal means to recover our money and obtain justice.”

Last week Rathnayaka admitted in a telephone interview that he had received cash and money transfers amounting to more than £7,000 from the Britons. He said the money was for police bail and for a payment to a figure he called “Little Big Man” who could withdraw the case against them.

“In Thailand everyone knows it’s like that,” he said. “They can go to jail or they can just pay a fine and go home. It is corruption, you know?”

Rathnayaka also agreed that the “bail” — about £4,000 — was never returned to Ingram and Xi. Thai law says bail should be refunded.

In a detailed statement the couple said they were first detained at an airport office of the tourist police and later taken to cells at a police station in an isolated modern building on the fringes of the airport.

Rathnayaka confirmed that he met them in the cells on the morning of Sunday, April 26, and arranged the “bail”. The police kept the couple’s passports. Rathnayaka then escorted Ingram and Xi to the Valentine Resort, a lurid pink motel a few hundred yards from the runways. They were to remain there for four days.

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