ART DETECTIVE:Niamh O'Sullivan has spent 15 years researching the life of Irish artist Aloysius O'Kelly, and her breakthroughs came from paintings that were stashed in attics around the world

YOU KNOW THOSE stories about finding a painting in the attic that turns out to be a lost masterpiece? Don’t write them off. They really do happen. Art history is not a done deal, but a house of many mansions – some of which are only now being cleared of dust, cobwebs and general confusion.

Take the 19th-century painter Aloysius O’Kelly, for instance. Niamh O’Sullivan, professor of visual culture at the National College of Art and Design (NCAD) in Dublin, has produced a fascinating and beautifully-produced biography of this enigmatic Irish artist, which runs to more than 300 pages.

Yet when she began work on the project, she barely had enough material to cover a postcard. “There was almost no trace of him to be found at all,” she says. “No letter, no descendants that anybody knew about.” As O’Sullivan prepared to track her quarry on three continents, the reason for all the secrecy soon became apparent. O’Kelly was the youngest of four brothers, all of whom had strong Fenian sympathies. His eldest brother, James, in particular, was a lifelong political activist who was forever trying to slip beneath official radars of one kind and another.

Theirs were the kind of circles in which letters were written in elaborate codes – and then destroyed. And sadly for O’Sullivan, they liked changing their names. “It’s the nightmare of all nightmares if you’re doing a biography,” she says. “He was born Kelly. Then all the brothers changed to O’Kelly, which they felt was a more national-sounding name; and he followed suit.”

A talented young painter who studied at the École des Beaux Arts in Paris, Aloysius O’Kelly exhibited in Dublin, London, Paris, New York, Chicago, Washington and Boston. “I went through 60 years’ worth of catalogues for each of those venues – which amounted to 900 catalogues,” O’Sullivan recalls with a grimace.

"On the last day, when I finished the last catalogue, I was in the National Library in London. I just sort of leaned back – phew, that's that done – and then, out of the corner of my eye, I saw the same address and sortof of the same name."

At first she thought she was seeing things. In fact, Aloysius O’Kelly had, somewhat wittily, adopted the name Arthur Oakley. “So I had to do all 900 catalogues again,” says O’Sullivan.

No sooner had she finished than she had a call from an Egyptian carpet dealer to say that he had a painting by an artist called Kelly. Could it be the same man? “I said ‘No, I don’t think so. Send me a photograph.’ But yes, it was.”

She returned to the catalogues for a third time. Luckily, she says, her family helped. “I have a wonderful sister in New York who would go and check things for me. And a very elderly aunt here in Dublin who’d occasionally go into the National Library. She’s now 95 and sadly, she’s not up to knowing that the book has been published. She would so love to have seen it.”

Given the elusive nature of the material – even the painter’s date of death wasn’t known until she tracked it down – O’Sullivan’s persistence in researching Aloysius O’Kelly over a period of some 15 years is remarkable.

Did she never feel like giving up? “Well, there were a lot of gaps,” she says. “Initially, I did my PhD on him. Then I had two children and a job here in the NCAD, and I was very involved in setting up the Irish Film Centre, and various other things. So it would go into abeyance for many a year and then I’d go back to it. There were times when I nearly gave up. But he’s unique among 19th-century Irish painters. There’s nobody like him. So in a sense, it was too good to give up.”

O’Kelly’s life story contains several chapters which, if they were placed in a historical crime novel, would be decried as being OTT. Born in Dublin, near Westland Row church, in 1853, he grew up in London. In the 1870s, while he was an art student in Paris, he lived under the same roof as “Mrs A O’Kelly” and her baby son. She wasn’t his wife, however: she was an American teenager who had been seduced by his brother, James.

In the 1880s, Aloysius and James went to Egypt and the Sudan, where they got involved with the Mahdi’s independence movement in an attempt to distract British eyes from preparations for a revolution in Ireland. All of this, and much more, is detailed in O’Sullivan’s book, along with magnificent reproductions of O’Kelly’s work. O’Sullivan got several lucky breaks during the research process. In 1999, after she curated an exhibition of O’Kelly’s work at the Hugh Lane Gallery, she was contacted by James Nadal, a great-grand-nephew of O’Kelly’s. “He had paintings in the garage and in cupboards and everything else. He had 23.”

There was one particular painting, however, which O'Sullivan wanted to find – and it seemed to have vanished. It was called Mass in a Connemara Cabin. "I had a line drawing of it, so I knew what I was looking for," she says. "But I had resigned myself to not finding it." She was in the US when she got a call from a priest in Edinburgh to say he had a painting in his sitting-room signed Aloysius O'Kelly. He'd gone on the internet, seen an article by O'Sullivan about the missing masterpiece, and he was wondering if . . . ?

O’Sullivan was sceptical, but went to Edinburgh to have a look. “And there it was, in its extraordinary splendour.” The archbishop of Edinburgh decided to give the painting on long-term loan to the National Gallery where, she says, it will probably stay. Another O’Kelly painting turned up in an attic in Boston, where it had been stashed for more than half a century. “It was in spectacular condition,” says O’Sullivan. “I’ve never seen an oil painting with that kind of vibrancy and pristine colour. It was superb.”

So get hunting. You never know what might be underneath that mountain of National Geographicsand almost-usable electronic equipment. Just make sure you check the signature before you make any excited phone calls.

Aloysius O'Kelly: Art, Nation, Empireby Niamh O'Sullivan (Field Day Publications/University of Notre Dame, £35)