In 1901–1902, the Admiralty developed scout cruisers to work with destroyer flotillas, leading their torpedo attacks and backing them up when attacked by other destroyers. In May 1902, it requested tenders for a design that was capable of, a protective deck, a range of and an armament of six quick-firing 12-pounder 18 cwt guns, eight QF 3-pounder guns and two 18-inch torpedo tubes. It accepted four of the submissions and ordered one ship from each builder in the 1902–1903 Naval Programme and a repeat in the following year's programme. The two ships from Cammell Laird became the Pathfinder class. Four more 12-pounders were added to the specification in August. The ships had a length between perpendiculars of, a beam of and a draught of at deep load. They displaced at normal load and at deep load. Their crew consisted of 289 officers and ratings. The Pathfinder-class ships were powered by a pair of four-cylinder triple-expansion steam engines, each driving one shaft, using steam provided by a dozen Laird-Normand boilers that exhausted into three funnels. The engines were designed to produce a total of which was intended to give a maximum speed of 25 knots. Pathfinder slightly exceeded her design speed when she ran her sea trials in 1905. The scout cruisers soon proved too slow for this role as newer destroyers outpaced them. The sisters carried a maximum of of coal which gave them a range of at. The main armament of the Pathfinder class consisted of ten QF 12-pounder 18-cwt guns. Three guns were mounted abreast on the forecastle and the quarterdeck, with the remaining four guns positioned port and starboardamidships. They also carried eight QF 3-pounder Hotchkiss guns and two single mounts for 18-inch torpedo tubes, one on each broadside. The ships' protective deck armour ranged in thickness from and the conning tower had armour inches thick. They had a waterline belt thick.
Ships
Service
The sisters were in reserve for most of the first decade of their existence. After the beginning of the First World War in August 1914, they was assigned to coastal defence duties on the East Coast of England. Patrol was badly damaged during the German bombardment of Hartlepool in mid-December 1914 when she attempted to exit the harbour during the bombardment. After repairs were completed she remained on coast defence duties until she was transferred to the Irish Sea in 1918. The ship was paid off in 1919 and sold for scrap in 1920. Pathfinder was originally to have been named Fastnet but the name was changed before construction was started. Leader of the 8th Destroyer Flotilla, she was torpedoed and sunk by the German submarine U-21 in the approaches to the Firth of Forth on 5 August 1914 with the loss of 259 men, giving her the distinction of being the first warship sunk by a submarine.