IT was one of the most enduring partnerships in show business -- the calm manager and the mercurial but feisty Sinead O' Connor.

But the Nothing Compares 2 U singer has now parted ways with her long-term manager, and former lover, Fachtna O Ceallaigh. The working relationship between the music maestro, who is credited with steering her to international success, was said to have ended while O'Connor was on tour in Germany.

A source explained: "Fachtna received a very colourful email from Sinead. And things deteriorated after that.

"He was very upset about the whole thing. But he's an impressive manager with huge talent, he is incredibly well respected within the industry. He'll be okay."

When asked by the Sunday Independent if he represented O'Connor anymore, O Ceallaigh replied: "I don't have a client. I don't represent anyone that you are talking about."

The split brings to an end a 25-year partnership that saw O'Connor rise from a relative unknown to a singer, forever immortalised in a black-and-white video of the Prince classic she covered. She first met O Ceallaigh, a former Evening Press journalist, after she moved to London with dreams of a recording contract in the late Eighties.

The singer was soon signed up by Ensign Records, which released her 1987 debut album The Lion and the Cobra.

"I was 17 when I met Fachtna," O'Connor said in a previous interview.

"He was nearly 40 but we were both very driven people and you can see that from what we achieved together."

Afterwards O'Connor and O Ceallaigh began a love affair, despite their considerable age difference. The couple went through a break up around the time of Nothing Compares 2 U and the close-ups of her crying in the video were said to be attributed to the breakdown of the relationship with Fachtna.

They eventually rekindled their relationship in 2008.

O'Connor said afterwards: "Unfortunately when that [her relationship with O Ceallaigh] broke down, we allowed our working relationship to break down too and I think we have always regretted that. In my own case I don't think I would have got into nearly as much trouble if Fachtna had remained my manager."

Trouble included a concert in New Jersey in 1990 when O'Connor refused to set foot onstage if the American national anthem was played, prompting Frank Sinatra to threaten that he would "kick her ass". She also ripped up a picture of the Pope on US TV show Saturday Night Live in 1992 and declared on MTV that the US and England had a history of terrorism "no better than Saddam Hussein".

It has been a stormy time for the singer, and it was recently reported she is back with husband drug counsellor Barry Herridge after posting on her website she was leaving show business for health reasons. The couple have had an on-off relationship after their 'quickie' marriage in Las Vegas last December.

(c) 2012 Independent