Police and social services were baffled when an elderly man with an American accent was found lost on the streets of the English city of Hereford. He didn't know who he was or have any ID, and he was dressed in brand new clothes from Tesco. The quest to find out who he was had results that nobody could have predicted.

It was 7 November 2015 when the man was found in a bus station car park. Tests at the county hospital showed why he wasn't able to reveal his identity - he had dementia.

Sgt Sarah Bennett, from West Mercia police, was tasked with finding out who the mystery man was.

She initially assumed it would be a formality. Dementia patients regularly go missing and most are found in hours. But when she checked missing persons' reports locally she couldn't find anybody listed matching his description, so she expanded her search nationwide.

Image caption The abandoned man in hospital

Police trawled through CCTV, launched an appeal through the press appeal, contacted the national crime agency and Interpol.

Missing persons' databases in the UK and abroad were checked and the Canadian and US authorities were contacted. Nothing.

While in hospital the man was repeatedly asked his name. Once, and once only, he replied "Roger Curry." The police were aware it might not be his name at all - it might, for example, be someone from his past.

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Even so, he was called Roger by staff of the residential nursing home he was moved to while investigations continued.

Months passed, but the police still had no idea who Roger really was. They looked at a number of possibilities. Was he being cared for by someone locally and something happened to the carer? Had they died and Roger simply wandered off?

"We have a person. We have a possible name but we have nothing else. We have no identity documents - no indication of where he's from," said Sgt Bennett.

Image caption Amanda Bow with Roger in the nursing home

One afternoon in March 2016 I visited Roger at the nursing home. He looked content, even though he was clearly lost in his own world. I asked him his name and where he was from. But the questions, never mind the answers, were beyond him. He seemed a gentle sort, just very lost.

Roger was clearly well looked after. Staff had fallen in love with this gentleman who enjoyed chocolate muffins and the odd sherry at night.

Amanda Bow, the manager of the nursing home, said that they'd learned nothing about Roger since he arrived there.

"He's a blank canvas, completely blank," she told me. But she said tears would be shed if he was eventually identified and had to leave. "It'll be devastating, because he's our Roger. We've adopted him."

Image caption Darragh MacIntyre with Jim - a former classmate of Earl Roger Curry - and his wife Helen

Shortly after, a BBC Midlands news bulletin put out a fresh appeal.

It led to the first breakthrough.

The report had a big response from viewers and inspired a small army of social media sleuths to investigate. One post on a BBC Facebook page was particularly intriguing.

A woman called Debbie Cocker posted a photograph of a man called Earl Roger Curry, from a 1958 US high school yearbook. The photograph was of an 18-year-old man. He looked a bit like Roger and was about the same age.

Image caption Roger Curry in his 1958 high school yearbook

The yearbook picture was from Edmonds High School. Edmonds is just north of Seattle, in the northwest state of Washington.

I travelled there to meet a woman called Helen who looked after the web pages for the class of 1958 Edmonds High School. Helen was in the same school year as Roger, and her husband Jim was in the same class.

Both Helen and Jim believed that young man in the yearbook picture was the same person as the unknown man in the English nursing home.

Over the next weeks, I traced Earl Roger Curry down the US west coast to a house in Los Angeles, in an area called Whittier. It's a classic American suburb (the movie Back To The Future was filmed there), and the street where I believed Roger lived was the very picture of middle-class respectability.

But Earl Roger Curry's house stood out - an eyesore in an otherwise prosperous area. It had been badly damaged by fire and abandoned.

Image caption The Currys' fire-damaged house

Jerry Maiques lives opposite the old Curry home. I showed him pictures of Roger taken in the nursing home in England.

"That's Roger." No hesitation. "No question about it. No doubt." Another neighbour also recognised Roger.

It was the end of the search, but it marked the start of another mission - to find out how Roger was apparently abandoned halfway around the world. No-one here imagined that he could have travelled to England on his own.

Roger was married with two grown-up children, but trouble and illness had haunted the family

Everyone we spoke to had only good things to say about Roger. Another neighbour, Jennifer Apon, said: "I'd see him come and go from work. He would wear white scrubs, so I knew he was a nurse."

She liked him: "He just seemed like a very wonderful, kind family man and I just had a very good feeling around him."

The more we talked the more we learned. Roger was married with two grown-up children, but trouble and illness had haunted the family. Apart from Roger's dementia, his wife Mary Jo is also unwell. Their son Kevin acted as their carer in recent years but not so long ago he hadn't been welcome at the family home.

Zania, a neighbour, described the relationship between Kevin and his parents as "volatile".

"You could hear him [Kevin] at all different hours of the night just pounding on their door trying to get in screaming and yelling at them profanities, we worried for their safety," she said.

In 2014 their home was badly damaged in a fire and fenced off by the local authorities. No-one was home at the time of the fire but Roger and his wife moved out - the neighbours didn't see them again until one sweltering August morning in 2015.

Image caption Jerry Maiques, a neighbour of the Currys

Shortly after 06:00, Jerry saw Roger walking aimlessly behind the chain link fence guarding the family home. Jerry climbed the fence only to find Mary Jo lying on an inflatable mattress outside in the backyard of the burnt-out house.

A cool box packed with food and water was close by. It had been 32 degrees the previous day. Another hot day was forecast. The couple were locked behind the fence and couldn't get out, so Jerry called the police.

It emerged that Kevin had been bringing them food and he was suspected of locking them in behind the gate. But Kevin wasn't prosecuted. His mom told police it was her idea. They took no further action.

All this happened just three months before Roger was found in England.

While I was talking to Jerry outside his home, he spotted Roger's son Kevin, and his mother Mary Jo, parking across the street. We registered the alarm on her face. She looked frightened. Kevin stared, then they drove off quickly.

Image caption Kevin Curry

It emerged that Kevin was a complicated character. A restraining order was taken against him 17 years ago by his father. Did Kevin abandon his father in Britain?

It's not unheard of in the States. They call it "granny dumping" - abandoning your elderly relatives to avoid the costly medical bills.

I phoned Kevin. I wrote to him. He didn't get back to me. But I did manage to find his sister, Jeanette, who I knew had been estranged from the family for some years.

The 27-year-old was upset when I told her about her father. She knew nothing about him turning up in England but thought Kevin could have arranged it. Her biggest worry though was that he might be returned to LA. As far as she was concerned he was safe and well in Britain.

Back in the UK, the authorities were brought up to date about these new facts. Within two days a man was arrested in England. US social services and the FBI joined the investigation.

Then in July 2016, Roger Curry was taken from the nursing home he'd been staying in for the previous eight months and quietly flown back to the US.

A few weeks ago I flew back to Los Angeles.

Roger was now living in a nursing home a few miles from his Los Angeles home. I walked straight in but nearly didn't recognise him. He appeared dishevelled - unwashed and thinner than I remembered.

Media playback is unsupported on your device Media caption Roger's son Kevin wouldn't speak to the BBC on camera

He also had what appeared to be a cut on the crown of his head. When I visited a second time he looked better. Shaven and washed. But again I had walked in - unchallenged - and there didn't seem to be anything to stop Roger wandering away.

I still didn't know how he travelled to Britain in the first place, but I believed his son, Kevin knew the truth. I eventually found him at the remains of the family home. He ran and hid in the property before later agreeing to answer my questions.

He called me inside the fence to talk but what he told me made little sense. He denied that he had anything to do with the abandonment of his father in England. He said his father became ill when they were visiting England on a holiday and that he asked someone to take him to hospital.

But this account didn't add up. Why hadn't he tried to find his father all those months he was in care? When he later emerged from behind the fence he'd pulled his jacket hood over his face. I asked him again for one proper interview but he accused me of harassing him before driving off - very slowly, because he couldn't see where he was going. It was the strangest of getaways.

Roger's future is now being decided by US courts. The Los Angeles authorities have taken control of his care. That's being challenged by Kevin and his mother but the legal papers show that the authorities accuse them of taking Roger to the UK and abandoning him there.

We now know that all three flew into the UK in November 2015, but only two flew home. An elderly and vulnerable man was dumped overseas by his family.

The mystery has been solved. But this isn't the ending to Roger's story that anybody expected or even wanted. And now - as Roger faces an unknown future - I'm left wondering whether he'd have been better off had his identity been left undiscovered.

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