During both World Wars, Scapa Flow in the Orkney archipelago was used as a naval anchorage for the British fleet. To protect the southern entrance to the anchorage, gun batteries were established at Hoxa Head and on the island of Flotta.
At Hoxa, concrete buildings, foundation and plinths still remain, most relating to the World War 2 military occupation. It was thought the main threat would come from German submarines and fast motor torpedo boats. An anti-submarine net barrier slung between Hoxa and Flotta would have deterred any submerged submarine whilst electric induction loops and searchlights would have detected any surface intrusion.
Once detected any enemy ships would have been shelled by the twin 6-pounder (57mm) artillery guns firing at a rate of 72 rounds per minute. This firepower would produce a lot of smoke so the control tower had to be built two stories high above the guns.
The guns were never fired in anger.