Sky News sources tonight claimed that Anne Darwin had confessed to knowing her husband was alive during that period.

John Darwin was arrested in Basingstoke, Hampshire, where he was staying at the home of his son Anthony, 29.

Darwin, from Cleveland, walked into a London police station on Saturday appearing tanned and claiming to be a missing person who had lost his memory.

Cleveland Police, who are leading the investigation, said they would be examining photographs that allegedly show Darwin with his wife in Panama City in July 2006.

Detective Superintendent Tony Hutchinson said: "That is one line of inquiry we will be following." But he added: "Photographs can be doctored."

A couple named John and Anne were shown on the Move to Panama website with the firm's boss, Mario Vilar. Vilar has said they did not use the surname Darwin.

Hutchinson said police had no immediate plans to extradite Anne Darwin or to travel to Panama to interview her.

Hutchinson said Darwin's reappearance had "raised a lot of questions". He said: "We needed to speak to John Darwin - clearly it's only right and proper that we spoke to him under caution." He confirmed that Darwin would be medically examined. "He may have been suffering from amnesia for five and half years," he said.

Hutchinson made a public appeal for information, telling reporters: "We want to piece together exactly where he's been since he went missing in 2002."

Asked whether the investigation was being led by the media, Hutchinson said journalists had more "latitude" than the police, and added: "The press have certainly been providing us with a lot of information."

Hutchinson confirmed that the police had been told of a possible financial link between Darwin and Panama three months ago.

Anne Darwin yesterday told reporters she had believed her husband dead and had claimed in "good faith" on his life insurance.

She moved to Panama City six weeks ago after selling the couple's two homes in Seaton Carew, but has now said she hopes to fly back to Britain to see her husband.

Yesterday the force appealed for anyone who had lived near or worked with John Darwin in the last five years to contact them.

He disappeared after paddling out to sea in a red canoe in Seaton Carew, near Hartlepool. The following year an inquest was held into his assumed death.

Anne Darwin, 55, had initially said she first heard from her husband in a phone call on Saturday night. When he came on the line he told her he could not remember anything since a holiday to Norway in 2000.

"There must have been an accident when he went out on the canoe. He must have hit his head or something," she told reporters.

She said the insurance payouts that she claimed "in good faith" after her husband was declared dead by a coroner in 2003 may now have to be repaid.

John Darwin worked as a science and maths teacher, then for a bank and, at the time of his disappearance, was a prison officer at Holme House jail, Stockton-on-Tees.