On the 15th of April, the world watched on in horror as one of France's most famous landmarks, Notre-Dame Cathedral caught alight. The Cathedral had stood for more than 800 years, through revolutions and world wars, but as the flames took hold, the architectural icon was in peril. What took place over the next nine hours was an epic battle by some 400 firefighters to save the building. In this dramatic film, those leading the operation explain how events unfolded.