In January 1972, a peaceful civil rights march in Northern Ireland ended in bloodshed. Troops from Britain's 1st Battalion Parachute Regiment opened fire on marchers, leaving 13 dead and 15 wounded. Seven of those killed were teenage boys. The day became known as 'Bloody Sunday'. The events occurred in broad daylight and in the full glare of the press. Within hours, the British military informed the world that they had won an 'IRA gun battle'. This became the official narrative for decades until a family-led campaign instigated one of the most complex inquiries in history.