This, then, was one of the units on the Outer Hebrides and Iceland patrol during the winter of 1915, and they seemed to be the sole occupants of the leagues of water around. It was barely eleven o'clock, Greenwich time, when they reached the last ten miles of their beat, and speed was reduced so that they would not have to turn about and begin steaming back over the course they had come until the morning watch went below at midday. This was an artful though harmless arrangement to enable those going off duty to have a meal and at least an hour's rest in peace, as on the voyage back both wind and sea would be astern and the vicious lurching of the small ship reduced to a minimum. The time passed slowly, as it generally did on patrol when nothing exciting was afoot, but a few minutes before the awaited eight bells the officer on duty snatched up the binoculars, and almost simultaneously the look-out gave a warning shout which caused the attention of everyone on deck to suddenly become strained. Away to port, less than half-a-mile distant, the thin grey tube of a periscope could be seen planing through the waves, with a fringe of white foam blowing from its base. There was a hoarse cry down the fo'c'sle hatch for "All hands on deck!" The telegraph tinkled for "Full ahead!" A signal was made to the ships astern for concerted action. The gun was manned, and the leading trawler, now cleared for action, headed towards her under-water opponent. The other two vessels of the unit put on speed and spread out until all three were line-abreast and about two cables apart. In this formation the chase was maintained for some twenty minutes, when a second submarine appeared above the surface away to starboard. She appeared to be a large vessel and would probably have turned the scale at 1000 tons. It was at this early stage in the action that the mistake was made. The leading trawler immediately opened fire, but the range was considerable and the shells fell short. Signalling to the other two trawlers to continue the chase of the first submarine sighted, she headed straight for the largest of the two hostile craft to engage her at close range. While this was in progress the first submarine came to the surface and proved to be also a larger craft than had been anticipated. The two trawlers chasing her immediately opened fire, but her superior surface speed soon placed her out of range of the comparatively small guns then carried by the trawler patrols. Now came the surprise. Almost simultaneously the two submarines opened fire from heavy guns. The shells at first fell wide, but in a moment the British officers realised that they were outranged, for whereas their shells were falling short, those from the enemy whistled over their heads and ploughed up columns of white water over a cable's length astern.