The Mersey class was a class of Admiralty naval trawlers built for the Royal Navy (or other government institutions) prior to World War II.

[2] Admiralty meant they were built for military service as opposed to conversions of existing boats.

Some were completed as fishing vessels rather than for military service.

Many went on to be used in various roles during World War II.

The Mersey-class trawlers were purpose-built to a standard Admiralty design intended for patrol, anti-submarine and minesweeping roles.

HMT John Quilliam, delivered in June 1917, was the first of the standard completions.

Propulsion was a three cylinder triple expansion steam engine, powered from a single boiler, and delivering nominal 87 horsepower (600 indicated horsepower) The smallest of the non-standard ships measured 36.8 metres (120 ft 9 in) in length with a 6.71 m (22 ft 0 in) beam.

For the Mersey-class the HMT prefix meant "His Majesty’s Trawler" but HMT was also used for vessels taken into Sea Transport Service as transports ("Hired Military Transport", though often referred to as “His Majesty’s Troopship”) and His Majesty’s Tug,.

Renamed Nith September 1920, Excellent June 1922.

Armament: 1 × QF 12-per 12 cwt gun.

Loaned September 1921 to June 1934 to South African Navy as Sonneblom.

Armament: 1x QF 12-pounder 12 cwt naval gun, 1x Depth-charge thrower and mechanical minesweeping gear: Crew: 15, up to 18 with wireless.