One Batch 1 (HMS Clyde), which was the Falklands guard ship, was decommissioned and transferred at the end of its lease to the Royal Bahrain Naval Force.

The five new Batch 2 ships provide overseas forward presence, performing maritime security duties and disaster relief operations, often supported by a Royal Fleet Auxiliary vessel.

In early 2001, the Ministry of Defence placed an order with Vosper Thornycroft (VT) for three River-class offshore patrol vessels to replace the Island class.

[2][22] The River class are significantly larger than the Island-class vessels and have a large open deck aft allowing them to be fitted with equipment for a specific role, which can include fire-fighting, disaster relief and anti-pollution work.

"[24] On 24 April 2017, in a written answer to a question raised by Sir Nicholas Soames, Parliamentary Under-Secretary for Defence Harriett Baldwin stated Severn would be decommissioned in 2017, with Mersey and Clyde following in 2019.

[27] In March 2018, Baldwin's successor as Parliamentary Under-Secretary for Defence, Guto Bebb, announced that £12.7m had been allocated from the "EU Exit Preparedness Fund" to maintain the three Batch 1 ships to control and enforce UK waters and fisheries following the United Kingdom's withdrawal from the European Union.

[2] This fourth ship, HMS Clyde (P257), was constructed at Portsmouth Dockyard and replaced the two Castle-class patrol vessels for duties around the South Atlantic and the Falkland Islands.

To fulfil this role, Clyde incorporates several modifications, including an extended length 81.5 m (267 ft 5 in) hull, a top speed of 21 knots (39 km/h; 24 mph), a 30 mm cannon, two miniguns and mountings for five general purpose machine guns.

[34] On 6 November 2013 it was announced that the British Government had signed an Agreement in Principle to build three new offshore patrol vessels, based on the River-class design, at a fixed price of £348 million including spares and support for the Royal Navy.

Replacing multiple large consoles dedicated to specific tasks with a single hardware solution reduces the number of spares required to be carried onboard and will significantly decrease through-life costs.

[41] A criticism of the class is that the reasoning behind their commissioning was simply to ensure that public money continued to support BAE dockyards and jobs prior to the ordering of the Type 26 frigate.

[43] The Royal Navy ships are built to more stringent naval standards, with features such as magazine protection, improved hull integrity and fire safety modifications, as well as greater redundancy.

[45][46] All Batch 2 ships will fulfil forward presence tasks, permanently stationed overseas with rotating crews, releasing the Type 23 frigates which previously filled the roles for other duties.

[50] The defence review suggested that the ships could be used to increase the Royal Navy's ability to defend UK interests at home and abroad.

[49] During a Defence Select Committee in July 2016, the First Sea Lord Admiral Sir Philip Jones indicated that the option for a fleet of "up to six" offshore patrol vessels had been reduced to five, with Clyde being replaced by HMS Forth, a new Batch 2 ship.

In January 2016 it was announced that a contract had been signed to provide the Royal Thai Navy with a second ship based on the River-class OPV to be built under licence at Bangkok Dock Company.

[61] This second Thai-built ship, HTMS Prachuap Khiri Khan was launched in August 2019 fitted with four RGM-84 Harpoon anti-ship missiles not present on Krabi.