One of the most iconic photographs of the Irish War of Independence has been revealed to be a still from a film.

For decades it was thought to show a key moment in Irish history.

It supposedly showed British intelligence officer Lt Gilbert Arthur Price shooting at the IRA, moments before he was killed in a gun battle on Dublin's Talbot Street on October 14, 1920.

The photograph was on the cover of  Dan Breen's book “My Fight for Irish Freedom” (1973) and more recently on the book “The War For Ireland 1913-1923” published just last year. It has been widely used in history books for close to ninety years.

The picture had long been attributed to John Horgan, then a 15-year-old apprentice photographer who went on to become famous.

However, research at the Irish Film Institute has revealed this dramatic picture is a still from a 1926 film called “Irish Destiny.”

It was the first movie set in Ireland about the War of Independence.

The hero of the film is an IRA man named O'Hara, played by Paddy Dunne Cullivan.

In the film, O'Hara is involved in a shootout with British forces. It is the  still from that scene that was  long thought to be a scene from a real shoot-out, and it has confused Irish historians for decades.

Historian Tommy Graham, editor of the magazine “History Ireland” says the mix-up happened  due to a newspaper article, which featured it among a series of pictures from the War of Independence.

A spokesman for Osprey Publishing, which produced “The War for Ireland: 1913-1923,” stated they was unaware of the real background of the picture it choose for the cover.

"It's a very striking image of the period. That was why we choose it," he told the Irish Independent.