Detectives began to investigate the disappearance of a prison officer who was presumed drowned in a canoeing accident at least three months before he walked into a police station to announce that he was still alive.

The Times has been told that officers from Cleveland Police contacted authorities in the North East in September over John Darwin’s disappearance at sea five years earlier. A legal source believes that the police were working on a theory that the married father of two, a former teacher who had amassed significant debts, may have been living in Panama.

It is also thought that by September officers had tentatively begun to investigate the disappearance of Mr Darwin. Detectives were preparing to conduct a detailed interview with Mr Darwin, now 57, who claimed — when he strolled into a London police station on Saturday evening looking fit and tanned — that he had lost his memory and had no knowledge of his whereabouts during the past 5½ years. His family say that he has no recollection of anything after 2000.

Police will want to know whether it is merely a coincidence that the apparent amnesiac’s extraordinary reappearance should come only six weeks after his “widow”, Anne Darwin, suddenly sold the family home in Seaton Carew, near Hartlepool, and left Britain to start a new life in Panama.

Speaking from her apartment in Panama City last night, Mrs Darwin admitted that she had already claimed the insurance money from his “death” and acknowledged she might now have to repay it.

Mrs Darwin, who said that she first visited Panama in 2005 and had since made several visits, said there had been no contact with her husband since his disappearance in March 2002. She said she had spoken to him three times since his reappearance on Saturday, adding that because of “visa issues” she had no immediate plans to return to Britain. She said that she had been “as amazed as anyone” to hear that he was still alive.

The questions of where he has been and how has he survived remained unanswered — and what really happened on March 21, 2002, when Mr Darwin took to the sea in his red canoe, a few hours before he was due to start a night shift at Holme House prison, Stockton-on-Tees. It was 12 hours before the former science teacher’s disappearance was reported, prompting a rescue operation that found no trace of him. The wreckage of his kayak was found on a beach six weeks later.

Mr Darwin, who once boasted that he would be a millionaire by the age of 50, liked to dabble in the stock market. He also owned more than a dozen buy-to-let properties in Co Durham.

It is understood that someone using the name John Darwin obtained a credit card in September last year. The application came from one of two adjoining properties that were jointly owned by the couple in Seaton Carew before they were transferred into the name of their elder son, Mark, in June 2006. It is known that Mark Darwin recently transferred several hundred thousand pounds — possibly the proceeds of the house sale — to a Panamanian account in his mother’s name.

The credit card application may have been a result of fraud by an outsider and is not proof of any wrongdoing on Mr or Mrs Darwin’s part, one credit expert said.

Mrs Darwin last night refused to answer questions from the Daily Mail about her financial situation.

In response to a suggestion her husband had faked his death because of financial problems she told the paper: “People can think what they want — I know the truth. Maybe all the speculation is to be expected. There was a lot of speculation after he disappeared.”

Despite claims that the couple were heavily in debt when Mr Darwin disappeared, there are no county court judgments against their names or against their former company, Eagle Enterprises. Police are believed to have been in touch with the high street bank HSBC after removing unopened letters from Mrs Darwin’s former house on Monday. HSBC declined to comment.

Yorkshire Bank, which provided a mortgage to the couple for their home in Seaton Carew, declined to say whether either Mr or Mrs Darwin had taken out an insurance policy with them or whether Cleveland Police had been in touch with their office.

The couple’s sons, Mark, 31, and Anthony, 29, issued a statement last night in which they claimed that their father had “no memory of events since June 2000”, 21 months before his disappearance. The brothers said that their father’s reappearance had “come as a huge shock to the whole family”. It added: “We are extremely happy that he is alive and we are looking forward to spending time with him.”

It is understood that Cleveland Police may have been alerted to a potential Central American connection by the recent decision of Mrs Darwin to emigrate to Panama. The doctor’s receptionist did not sell her Seaton Carew home until October this year. She said last night she hoped her husband would be able to join her in Panama, with which she had fallen in love, adding: “It is not the money I ever wanted — it was having my husband back.”

John Duffield, 37, who bought Mrs Darwin’s house for £295,000 in October, said that she had left behind a substantial amount of property including antique pine bedroom furniture, a leather three-piece suite and two computers with the hard drives removed.

She said last night it would be of no use to her in her new life. Since her departure, at least a dozen letters with a Panamanian postmark addressed to her have been delivered to the house. They included correspondence from at least two banks in Panama City.

Mr Darwin’s inquest was held, at the request of the missing man’s family, at Hartlepool County Court in April 2003. Malcom Donnelly, the Hartlepool Coroner, heard evidence from the police before recording an open verdict, which led to the issuing of a death certificate.

Mr Donnelly yesterday expressed his surprise that Mr Darwin had “apparently turned up safe and well”.

“When there is no body, I have to deal with the facts as they are presented to me,” he said. “I can recall other inquests that have been carried out without a body, but to have a man actually turn up alive after such a long period of time is unprecedented in this jurisdiction.” Mr Donnelly said that he had not yet officially been informed that Mr Darwin was alive. When that happened, the inquest findings would become “null and void”.

Where law stands

— John Darwin is likely to face an investigation as to whether there has been any attempt to gain property, namely money, by deception under section 15 of the Theft Act 1968 – by committing an insurance fraud (Frances Gibb writes)

— The money would be the insurance that his wife might have claimed when he was declared dead

— An offence can be committed even when the culprit intends that the fruits of the deception go to someone other than himself, according to Professor Gary Slapper, director of the Open University law programme

— John Stonehouse was prosecuted for this offence after he staged his death by drowning off the coast of Miami in 1974 and was later sentenced to seven years

— It is not an offence just to disappear, although faking a disappearance so as to avoid paying debts or some other contractual or legal family obligation would be

— Unless child abandonment is involved, the authorities do not usually interfere beyond making the initial thorough searches

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