On April 30, 1980, six heavily armed gunmen burst into the Iranian embassy on Princes Gate, overlooking Hyde Park in London. There they took 26 hostages, including embassy staff, visitors, and three British citizens. A tense six-day siege ensued as millions gathered around screens across the country to witness the longest news flash in British television history, in which police negotiators and psychiatrists sought a bloodless end to the standoff, while the SAS – hitherto an organisation shrouded in secrecy – laid plans for a daring rescue mission: Operation Nimrod. Drawing on unpublished source material, interviews with the SAS, and testimony from witnesses including hostages, negotiators, intelligence officers and the on-site psychiatrist, historian Ben Macintyre takes readers on a journey from the years and weeks of build-up on both sides, to the minute-by-minute account of the siege and rescue.