Two Failed Torpedo Attacks, Then a Terrible Explosion
Once through the channels U 47 was free and clear. Searching for a target, the submarine's crew found two: HMS Royal Oak and an old seaplane tender, the Pegasus (mis-identified as a battlecruiser in the darkness of the harbor).
Under the northern lights, the U-Boat approached the Revenge Class battleship, fully aware of her size and strength. It was now the morning of the 14th of October, and after taking careful aim, U 47 unleashed a spread of three lethal torpedoes at the battleship and supposed battlecruiser from three of the forward tubes (the fourth tube malfunctioned). The crew waited, watching, counting down the seconds it would take for the torpedoes to reach their targets...
And there was an explosion - but only one, and it was muffled. U 47 turned towards the exit to the harbor, fully expecting the British vessels to come alive and attack - and as the stern torpedo tube was unmasked by the vessel's turn, Gunther Prien ordered its torpedo fired at the targets while the forward tubes were reloaded, hoping that he might get another shot before the defenses began attacking.
This torpedo missed as well. But to the shock of U 47's crew, there was no response from the British. Unbeknownst to them, one of their torpedoes did hit HMS Royal Oak's bow, and tore a hole in it. But the crew of the massive ship simply assumed normally combustible items stored in this part of the ship had detonated, and those not engaged in managing the damage incurred went back to sleep.
U 47 turned in the night, and fired three more torpedoes. All struck the Royal Oak, and she exploded with a thunderous roar.