River-class patrol vessel

The River class is a British class of five offshore patrol vessels. Three were built for the Royal Navy, replacing the seven ships of the Island class, along with a fourth, a modified vessel based on the River class which replaced the Castle class, for duties in the Falklands. They are primarily used in the fisheries protection role. A fifth was built for the Royal Thai Navy.

Design
The ships 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. For this purpose, a 25 tonne capacity crane is fitted. In addition, the deck is strong enough for the transport of various tracked and wheeled light vehicles, or an LCVP.

Ownership
Initially the three ships were not owned by the Royal Navy. They were constructed under an arrangement with the shipbuilder, Vosper Thornycroft (VT), under which the Royal Navy leased the vessels from the shipbuilder for a period of ten years. VT were responsible for all maintenance and support for the ships during the charter period. At the end of this, the Navy could then either return the ships, renew the lease or purchase them outright.

In September 2012, it was announced by the Defence Secretary Philip Hammond that the Ministry of Defence had purchased the vessels for £39 million.

Modified River class
HMS Clyde: A modified fourth vessel, HMS Clyde, constructed at Portsmouth Dockyard, replaced the two vessels of the Castle-class for duties in the Falkland Islands. This ship displaces 1,850 tonnes and has a 30mm gun, as well as a deck strengthened for aircraft operations.

HTMS Krabi: Another vessel was built for the Royal Thai Navy called HTMS Krabi. This ship was built in Thailand but designed by BAE Systems. On this ship the main gun was changed to a 76mm gun.

Brazilian Navy
The Brazilian Navy's Amazonas-class corvettes, built by BAE in the United Kingdom, are based on the River-class design.

2013 Royal Navy order
On 6 November 2013 it was announced that the Royal Navy has ordered three further modified River-class vessels, to replace HM Ships Tyne, Severn and Mersey. The new batch is to be built at BAE's Clyde shipyards and will feature helicopter landing facilities. The first of the new ships is expected to enter service in 2017.