Norton, who grew up in Cork, is said to have been "visibly shocked" when he discovered how vicious some of his relatives were while fighting for the crown in the 18th century.

Taking part in the BBC's family history programme Who Do You Think You Are, Norton (44) reveals how he often believed that he and his family were made to feel like foreigners in Ireland because of their Protestant background.

"My dad worked at Guinness, the brewery, and I think he must have been a bit rubbish at his job, because they just kept transferring him all the time, " he said. "It wasn't until I was about 14 or 15 that we settled in a place called Bandon, Co Cork."

It is here, with his mother's family, that Norton begins tracing his ancestry on the programme, but he quickly comes up against dead-ends as it is revealed that his great-grandmother had two different maiden names. By trawling through parish church records, he eventually discovers that she was baptised Mary Logan and that her mother was Margaret Logan. His great-grandfather Fred Dooey remains a mystery as he attempted to remove his name from the baptism certificate of his first child, implying he may have believed he was not the father.

However, it is the background of Norton's father's family in Carnew, Co Wexford which shocks him the most when he discovers they brutally fought and killed their own countrymen in 1798. For the unfailingly mild-mannered Norton, this proved hard to believe, the programme shows.

Norton has always insisted he had a happy childhood in Cork, while at the same time admitting he spent almost all of his time watching TV. "Television was my friend, " he has said previously. "But I was quite happy about that. It would have irritated me if people had come around and interrupted my viewing habit."

In his first year studying at University College Cork, however, Norton had a breakdown and stayed in his room for weeks on end. Finally, believing that his homosexuality would never be accepted in Ireland, he fled to San Francisco and joined a commune.

"I was an Irish 20, which anywhere else in the world is about 14, " he has recalled. He has never lived long-term in Ireland since then and it is only now that he has decided to trace his family's roots.