In his Old Ireland in Colour project at the Insight SFI Research Centre at NUI Galway, Professor John Breslin uses DeOldify, an open source tool, to bring colour to archive images. This image, taken on the 25th of May 1921, shows Dublin's Custom House, home to the British-controlled Local Government Board, in flames after it was set ablaze by the IRA. 

Dáil Éireann's propaganda department defended the Custom House attack, saying "the lives of four million people are a more sacred charge than any architectural masterpiece". 

So how did Breslin approach this photo? "I used a number of colourisers here to get more realistic looking flames in the windows," he says. "I also touched up the image to remove marks and scratches as well as the photographer's studio name. Some blemishes were fixed through the clone tool in Photoshop  - bars in the railings, bricks, etc."

Original image courtesy of the National Library of Ireland