A rare photograph of Michael Collins has been found in the attic of a suburban Dublin home 90 years after the Irish leader's death.

According to the Irish Independent, the photo shows Collins officiating at the wedding of fellow IRA man Paddy O'Donoghue in June 1919, five months after the start of the War of Independence. Only two months before the picture was taken Collins had infiltrated Great Brunswick (Pearse) Street police barracks with his spy, Ned Broy. At the time of the photo, Collins was on the run with a £10,000 bounty on his head.

There are no copies of the photograph in the National Archive, and Adams, the prestigious auctioneers who run an annual sale of War of Independence memorabilia, told the Sunday Independent that they had never seen the photograph before.

Said valuer and memorabilia expert Kieran O'Boyle: "It's a lovely picture. Collins is fresh-faced and is not attempting to hide from the camera."

"One of the myths about Collins was that Dublin Castle had no photographs of him. They did, but they were of poor quality. They would have given their eye teeth for this."

"He was wanted dead or alive, so he was exceptionally brave—and trusting—to face a photographer's lens in this manner," said O'Boyle.

He added that Collins memorabilia is always in high demand.

"In 2011, we sold an archive of Collins's handwritten letters to his sister Hannie for just over €240,000.

"This photo could potentially sell for thousands to the right collector."

Writer and broadcaster Dave Kenny discovered the rare photograph in an old sea-chest.

"I found it when I was going through my late father's papers. It's in great condition. What makes it so unique is that Collins is looking directly at the camera—something he never did during the war period," said Kenny.

"In other photos, like the iconic one of Tom Barry's wedding at Vaughan's Hotel, Collins deliberately blurred his image by nodding his head.

"If the British had had a copy of this photo, then Collins wouldn't have lasted long on the streets of Dublin," he added. "He would have had to rethink his strategy of operating in the open.

"He could well have been captured and shot.

"Who knows how things might have panned out then? Would we have won our independence without Collins? Arguably yes, but at a much later date.

"On top of that, the groom was also wanted by the British. Paddy was the head of the IRA in Manchester and helped Eamon de Valera escape from Lincoln Gaol four months before the photo was taken. He later founded Shelbourne Park greyhound stadium."

The bride, Violet Gore, signed the photograph to Mr Kenny's grandmother, 'Gypsy' and her sister Maire Nic Shiubhlaigh. The Independent reports that the sisters were co-founders of The Abbey Theatre and ardent nationalists who saw action in 1916, with Maire leading Cumann na mBan under Thomas McDonagh and Gypsy carrying dispatches for Cathal Brugha.

"After the war, Maire married Collins's close friend and comrade Major General Bob Price. Bob had been director of organisation on the GHQ staff of the IRA. My great-grandfather -- who published the Irish War News for Pearse in 1916 -- was also friendly with Collins. They were both members of the IRB," said Kenny who is currently writing a book about his family.

The picture stayed in the possession of Mr Kenny's family throughout the War of Independence.

"It could have been discovered at any stage as the family home and printing business were constantly raided by the police. I like to imagine the Black and Tans ransacking their house in Glasthule, with Collins staring down at them from the wall."

Kenny decided to share the picture for the 90th anniversary of Beal na mBlath this week.

"It's a rare shot of our greatest national hero taking a day off from scrapping with the British Empire.

"I felt people should see it. I still haven't decided what to do with it though. I contacted the National Photographic Archive and they don't have a copy. I also brought it to Adams Auctioneers.

"They gave me a valuation which made my eyes water as it is, in effect, just an old wedding photograph.

"I wouldn't like to sell it, but if the right offer came in ... Either way, it was a lovely thing to find in the attic."