text: In 2005, at the age of 13, he won the role of Riccio in The Thief Lord, the film adaptation of Cornelia Funke's best-selling children's novel. He was also cast in the lead role in Johnny and the Bomb, a BBC three-part television drama adapted from Terry Pratchett's novel of the same name. MacKay also had some work in television, including roles in Rose and Maloney, Footprints in the Snow and The Brief. In the 2008 film Defiance, MacKay played Aron, the youngest of the four Bielski brothers. In 2009 he portrayed Harry in The Boys Are Back starring Clive Owen. MacKay co-starred in the Marc Evans-directed musical film Hunky Dory opposite Minnie Driver, Aneurin Barnard and Kimberley Nixon, which is set in 1970s Swansea.
  2012–present
  In 2012, he played the main character, Private Tommo Peaceful, in Private Peaceful, and appeared as a paralyzed soldier in the inspirational film The Best of Men. In 2013, MacKay portrayed Eddie in How I Live Now opposite Saoirse Ronan and directed by Kevin Macdonald, and starred as Davy in the musical film Sunshine on Leith, featuring songs by The Proclaimers, directed by Dexter Fletcher. In 2014, MacKay played the role of Joe, a 20-year-old struggling to come out in a homophobic Britain in 1984 in the film Pride (based on a true story) also starring Bill Nighy.