When international superstar Donny Osmond told BBC Radio Wales' Nicola Heywood-Thomas live on air in November 2002 that he thought he had Welsh ancestry, the ears of archivists in Wales started buzzing with excitement.

Donny talks about his Welsh roots in 2002 (Need help?)

It didn't take long for tongues to start wagging too, as the experts set about the search to find out if it could be true.

It turns out Donny was right - the Osmond family can be traced back to Merthyr Tydfil as far back as 1585.

The singer couldn't resist an invitation to his family's homeland to find out more in a quest filmed for a BBC Wales TV special shown on St David's Day 2005. He was shocked to find there were parts of his family history he'd got entirely wrong.

And he was even more amazed to discover that some of his Merthyr Tydfil ancestors were also quite notorious in their own right.

Throughout a career spanning more than 30 years and 54 albums, Donny Osmond has always maintained that family is central to his life. Being of Mormon faith, he was already a follower of genealogy - an important part of the religion.

Although he had already done a huge amount of online research into his family tree, his Welsh roots had never been properly traced and much of the family's Welsh history was guesswork - much of it wrong.

In fact, the more archivists dug into the Osmond family history, the more interesting the story became.

BBC Wales' very own 'gene genie' Cat Whiteaway was given the job of leading the search to find Donny's Welsh roots.

"I was asked to find if there was any truth in what he'd said, and was given ten days to prove he was Welsh, although I managed it in less," she says.

"Because the Mormon Church has such strong family history ties, there was an awful lot of information available."

But although extensive Mormon records made the basic search relatively simple, finding more detailed history proved a challenge.

"Donny's mother Olive, who had died the previous year, was the link the Wales. And her maiden name was Davis, which was a blow - your heart drops when you come across a name as common as that," explains Cat.

"The Osmond name comes from Oxford, but Donny was more interested in exploring the Welsh line on his mother's side of the family. She'd already started a lot of family tree research in her lifetime and I think he wanted to carry that on.

"I'd normally start this sort of research with a birth certificate, but US data protection prevented me from doing that, so I had to use other resources.

"But once I started looking back through Olive's family tree, I found school records, work records, gravestones and houses where the ancestors had lived.

"We also found out occupations, and we've even managed to trace one of Donny's living relatives in Wales - Jane Cresswell, whose family is from Dowlais, and who now lives in St Athan.

"There were also a few surprises for him, and he wanted to know what they were. But we didn't want to give too much away - instead his reaction is caught on camera."

Producer Michael Lewis spent almost two years organising Donny's visit to Merthyr.

"For somebody who's an icon of our generation, it's incredible that his ancestors were also so important," he says.

"Many of them were involved in running Merthyr Steelworks, and one of his ancestors, Dr John Martin, was Chief Surgeon at the Steelworks, saving hundreds of lives throughout his career.

"It was a whirlwind visit, but Donny spent time talking to local people - there's a lovely scene where he's chatting to a pair of elderly gents over garden wall as if he's just the bloke delivering the bread!"

Donny enjoyed his visit to Merthyr so much, he returned to the town in June 2007 to perform an open-air concert at Cyfarthfa Castle.