As they prepare for their photoshoot at a swanky London hotel, with “make-up and hair” in attendance plus an entourage from Sony, the three men in dog collars seem slightly out of their depth. A cynic might easily conclude that these three singing priests are just the latest gimmick for a recession-hit music industry, desperate for some seasonal payola.

After all, these particular fathers come ready-packaged with twinkling eyes and great voices. The sincerity in their Ave Maria vibrato is almost palpable. And what do you know? More than 29,000 copies of their debut CD shifted last week in its first day of release, making it a likely contender for a Christmas No 1 in the UK album charts. The bosses at Sony, who have given this mini-God squad a recording deal worth £1.4m, will be opening their Advent calendars tomorrow morning with joy in their hearts.

Yet for all the high-level packaging, The Priests really are the genuine article, who deliver the classic church music they have always sung, from Ave Maria to O Holy Night, in perfect harmony. And this is no group hastily cobbled together by some slick marketeer. Eugene, 49, and Martin O’Hagan, 45 – they are brothers – grew up in a village just outside Londonderry in a large family for whom music and singing were natural pursuits. “Our mother, who died four years ago, nurtured music in us,” says Father Eugene. “When we were younger, we would always be called in to practise around the piano with her.”

Eugene was 18 when he decided to go into the priesthood. “It wasn’t like a Damascene conversion – it was more curiosity than anything else – and I didn’t have to fully commit before I was 27. It’s a bit like marriage: before you cross that threshold, there are no strings. Then the challenge is to live to that commitment.”

What about his singing talents, though? “Oh, some people said I should have gone on the stage,” says Father Eugene, (whose performance as Ko-Ko in an amateur production of The Mikado at the Buxton Festival last year won him best comic actor). “I’ve been tempted to think like that; but whenever I’m tempted, I also realise how lucky I am because I can incorporate singing into my work as a priest.”

What about Martin? “He felt called – not because I was his elder brother, but I think it helped having me to talk to.”

Meanwhile, their childhood friend David Delargy – now the 45-year-old baritone in the ensemble – was taking much the same route. One of six children, he too had been brought up in a family who enjoyed singsongs around the piano – in their case, in Ballymeena. “My dad loved to sing – Summertime from Porgy and Bess, or Some Enchanted Evening. It was just a hobby, really,” Father David tells me.

What about religion? “I grew up in a family where faith was practised and promoted. Our mother prayed with us each morning and night. Faith was passed on to us; it was part of the atmosphere we breathed.” He was 14 when he decided to become a priest.

And so when David and Martin met as boys in the same class at boarding school in Antrim, it was perhaps inevitable that they should end up singing together, along with big brother Eugene. Later, they all pitched up at the same Roman Catholic seminary, where the threesome was promptly dubbed “Holy, Holy, Holy”. Even after all three became priests, they carried on getting together to sing. At one point, while studying at the Gregorian University in Rome, they even sang a liturgy before Pope John Paul II.

They would have happily continued as a part-time local act. But then someone from Sony came across a demo tape from the trio, while searching for individual male voices for a Latin mass album. And almost immediately, the words “potentially one of the world’s biggest musical acts” started being muttered at executive levels.

Did being “discovered” bring on tears of grateful joy? Not exactly. The Priests are jolly chuffed with their album, and have clearly enjoyed meeting the likes of David Bailey (who apparently showed them a vaguely blasphemous artwork by Damien Hirst). They have no complaints about being made to take planes or stay in smart hotels, and they are looking forward to shovelling their end of the profits towards various charities. But they sing from a different hymn sheet to that of most pop stars.

Father Martin, a softly spoken man with amazingly big eyes and long lashes, hopes that their music will actually change us. “It might even enable people to put the brakes on, to stop and think: what is Christmas all about? They might even say: let’s forget the commerce and get back to what Christmas should be about. The collateral gain for us, as priests, is that the music might touch people’s hearts and make a difference to the way they look at the world. These are pieces that speak to the heart and the soul.”

They insisted that their recording contract contain a clause stating that their parochial duties will and must continue – whatever the success of the CD. Choosing a religious life is clearly no light commitment, wherever it is made; but choosing to become a Roman Catholic priest in Northern Ireland, at a time when religion often provided a trigger for appalling violence, required a different measure of resolution.

The Troubles were simply part of life, as far as the priests were concerned. In 1972, the village of Claudy, where Eugene and Martin grew up, was devastated by a no-warning IRA bomb. That day, their father, a potato inspector for the Ministry of Agriculture, had parked outside the Beaufort House hotel, beside the car in which the bomb was secreted.

“Our father missed being blown up by about four minutes,” says Father Eugene. “He was about a mile away when the bomb went up. Oh, we knew people who died. Kathryn Eakin [aged eight, she was cleaning the windows of the family grocery store], and a lady who served in the local shop.” In total, nine lost their lives.

Did the slaughter of innocents make him doubt his religious call-ing? “It wasn’t all about religion,” says Father Eugene. “There was a religious element to it, but our leaders played their part in bringing about resolution.” A canon lawyer, he has worked for years in marriage tribunals and says the majority of church weddings at which he officiates are now cross-denominational.

His brother Martin, he says, was called to administer the last rites to a young man fatally wounded during sectarian violence in Belfast. “Talking to me and fellow priests about it helped, but he was very upset,” Father Eugene recalls.

Father David had no less devastating experiences: a hold-up in the bank, in which he had to hit the floor; a gun pressed to his temple by some hoodlums who were trying to steal his car; three arson attacks at three churches; and worst of all, a murder close to home.

“I was teaching for about seven years at a diocesan grammar in Belfast,” he says. “And I shared a house with another priest. We had a housekeeper who would come in and make lunch for us – a lovely, warm person who loved to sing. I remember she’d sing Love Changes Everything by Andrew Lloyd Webber, and I would play it for her on the piano.

“She lived just outside Belfast in Dundonald. One Sunday night, I was at home, and I got a call to say her husband had been shot and would I come to the house. By the time I got there, she had been taken away by the police.”

Father David slowly relates the events of that terrible night. “Two men had come up on a motorbike. The passenger had dismounted, knocked on the door, and pushed past my housekeeper into her house. Our housekeeper’s husband was sitting on the sofa, having his supper and watching TV. He hadn’t been involved in anything. The gunman just shot him.

“By the time I got there, he was dead. I had to break the news to my housekeeper and her teenage son.” He sighs. “They were the only Catholic family in that street: that was the only reason.”

Did his ability to sing give him any solace? “Maybe you don’t think of music as a salve at the time, but it is. It can be a distraction.”

With such a hinterland, where death and violence left few lives untouched, the trio seem unlikely candidates for all the fuss and pantomime of press and publicity, the hoopla of the hit parade, the Bailey-directed shots for the album cover. Doesn’t it all seem like so much candyfloss?

“Showbiz life is only what you see through glossy magazines,” Father David says gently. “I don’t think that it’s half as glitzy as presented. I guess they have challenges to their lives that we don’t have – and those lives don’t always bring happiness. I get the impression that people in the music business work very, very hard. Sony is a place full of human beings with mortgages, and with children to get up in the morning. It’s stressful and pressurised and they eat at unusual times. Anyway, the only celebrities I have ever seen were in hotel corridors.”

Has the process of making the album involved any temptations, I wonder?

“Sometimes, you do have a ‘grass is greener’ experience,” says Father David. “But life isn’t a bed of roses, whatever path you take; and as life goes by, you grow into your life. I have always been secure that this was what God was calling me to do.”

Father Eugene, who seems more intrigued by the showbiz world, insists that he is content with the path he chose at 18. “I listen to, and have read about, the careers of many singers and actors. Like us, they incorporate their gifts into the humdrum of life. At the end, none of us can live at the height of the mountain all the time. Anyway, sometimes the humdrum is quite pleasant.”

The opportunity to sing to a wider audience has come about by divine providence, he believes. “We look at things through the prism of faith. An opportunity comes your way – and it doesn’t occur for no reason. You take a risk. Sometimes, the opportunity is worth it, because it is enriching.”

And I don’t think he’s referring to his royalties.

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