The waters around the Firth of Forth, close to the Isle of May, resembled a busy motorway on the misty evening of January 31, 1918. The entire Grand Fleet was heading for a major exercise at Scapa Flow, including 40 vessels from nearby Rosyth. Suspecting that a German U-boat was in the area, these ships showed only a dim stern light and maintained radio silence as they made their way at full speed to join the fleet.
Accompanying the battleships, cruisers and destroyers were two flotillas of K-class submarines - huge steam-powered vessels that were still proving their value as weapons of war. And it was when one of these ungainly craft veered out of line that the trouble began.
As K14 returned to the convoy, the following sub, K22, crashed into her. A coded message was at once sent to the leading cruiser, HMS Ithuriel, requesting that she turn back - at which point the battlecruiser Inflexible smashed into K22. There followed a succession of collisions as several more huge warships steamed into the area and into the path of the returning Ithuriel and her accompanying submarines. K17 was sunk by HMS Fearless, and HMS Australia narrowly missed K12, which headed straight for K6, forcing her to strike K4. As K4 sank with all crew on board, she was hit again, this time by K7. Another squadron of battleships and destroyers then entered the area, cutting down survivors who were struggling in the icy sea.
Today, a cairn at Anstruther commemorates what came to be called the Battle of May Island. But for the duration of the war, the incident was hushed up.
Which is hardly surprising when you consider that, within the space of 75 minutes, more than 100 people were killed and several vessels wrecked without a single enemy ship being present.