At 11.20 pm on Monday, 9 July, 1917 HMS Vanguard was at anchor in Scapa Flow. The mighty warship suddenly blew up, taking 804 of her crew down with her. An explosion had taken place in one of the two magazines which served turrets 'P' and 'Q'. It is believed that the cause of the explosion was the spontaneous detonation of cordite, which had become unstable. Although there is no specific evidence, it is thought that a fire in an adjacent compartment smouldered, undetected, long enough for some of the cordite near the adjoining bulkhead to overheat to dangerous levels. Just 3 of her crew survived the detonation.