Colbert, who hosted the Grammys at the weekend and made a recent Rolling Stone cover, once jokingly claimed to have been related to Athea's 1916 rebel Con Colbert, after whom the city's railway station is named.

But after being contacted by researchers working on a genealogy programme for PBS, Mr Browne helped them find details of Colbert's ancestors in St Mary's parish records in the city.

"They originally got in contact with a friend of mine in Dublin who is involved in the genealogy services. She got in touch with me and asked me to track down a Michael Gearon or Guerin in Limerick. I got on to Fr Donough O'Malley and we were able to find him on the parish register," explained Tony.

Parish records at St Mary's go back "at least 200 years", and one entry records the marriage of a Michael Gearon to Johanna Nicholson in January 1834.

"We found three children of that marriage, in 1836, 1838 and 1840, but one of the problems the show has is finding when exactly they went to America shortly after that," he said.

Records for emigrants disembarking at New York's Ellis Island, Tony said, weren't kept before the Famine and the researchers could not find any evidence there.

One of Tony's theories is that the Gearon family may have emigrated to Canada on one of the boats owned by Limerick merchant Francis Speight.

"Speight was a very wealthy operator who would sail up the St Lawrence and drop the emigrants off at Grosse Ile (where over 5,000 Irish emigrants who fled the Famine are buried) and would continue on to Quebec and bring back lumber to Limerick

"He wouldn't have cared less what the conditions for the emigrants were on board as long as he brought back his timber

"What we found when we tried to check this out was that the records at Grosse Ile only begin in the 1860s, the same as Ellis Island

"I'll have to wait to watch the programme to see if they found out what happened, but my guess is that they might have ended up in Canada and walked across the border as you could do back then. Stephen Colbert grew up in Carolina," said Tony.

PBS will broadcast the show in the United States on February 17, and Tony hopes to see footage shot of himself and Fr O'Malley browsing parish records. He also brought the crew to see Francis Speight's former residence on O'Connell Street.

He didn't bring them to Colbert Station, despite Stephen Colbert's claim to Fox News blowhard Bill O'Reilly that they were related. Mr Colbert, who pronounces his name with a silent "t" was blasted by Mr O'Reilly for frenchifying his name when "you're as Irish as me".