In May 1902, the British Admiralty issued an invitation to tender to several shipbuilding yards for a new type of small cruiser, intended to act as leaders for flotillas of destroyers.

[1] The Admiralty produced a broad specification for the ships, normal practice at the time for destroyers, requiring a speed of 25 knots (46 km/h; 29 mph), a range of 2,000 nautical miles (3,700 km; 2,300 mi), light armour and an armament of ten 12-pounder (3 inch, 76 mm) guns, eight 3-pounder (47mm) guns and two torpedo tubes.

[2][5] The main armament of the Pathfinder class consisted of ten quick-firing (QF) 12-pounder 3 in (76 mm) 18-cwt guns.

[7] On 8 February 1908, the torpedo gunboat Leda collided with the old cruiser Andromache in Harwich harbour and was holed, needing to be beached to avoid sinking.

[10] At the start of the First World War she was part of the 8th Destroyer Flotilla based at Rosyth in the Firth of Forth and commanded by Capt Francis Martin-Leake.

[11] Pathfinder was sunk off St. Abbs Head, Berwickshire, Scotland, on Saturday 5 September 1914 by the German U-21, commanded by Kapitänleutnant Otto Hersing.

At the beginning of September 1914, Otto Hersing, Commanding Officer of U-21, ventured to the Firth of Forth, home to the major British naval base at Rosyth.

At 1545 lookouts spotted a torpedo wake heading towards the starboard bow and the officer of the watch, Lieutenant-Commander Favell, attempted to take evasive action by ordering the starboard engine be put astern and the port engine at full ahead while the wheel was turned hard a port, the manoeuvre was not in time and the torpedo struck the ship beneath the bridge.

Broken in two, the Pathfinder instantly began sinking, dragging most of her crew down with her and leaving a massive pall of smoke to mark her grave.

The Captain and his secretary remained with the ship until the very end but somehow both survived"Also among the survivors was staff surgeon Thomas Aubrey Smyth, who lived at Bedeque House in Dromore, Co Down.

"I was then thrown forward by the slope of the deck and got jammed beneath a gun (which I expect is the cause of my bruising) and while in this position was carried down some way by the sinking ship, but fortunately after a time I became released and after what seemed like interminable ages I came to the surface, and after swimming a short time I was able to get an oar and some other floating material with the help of which I was just able to keep on the surface."

Despite the events of 5 September having been easily visible from shore, the authorities attempted to cover up the fact that Pathfinder had been sunk by a torpedo, insisting instead that it had struck a mine.

The reason for this is unclear, but probably has to do with the Admiralty's position that submarines — a still new and largely untested weapons platform — lacked the capacity to sink a surface warship with a torpedo.

A local paper, however, The Scotsman, published an eye-witness account by an Eyemouth fisherman, who had assisted in the rescue, that confirmed rumors that a submarine had been responsible.