The Royal Navy's Offshore Patrol Vessels (OPVs) are responsible for protecting the UK's interests both domestically and internationally.
They safeguard territorial waters, protect fishing stocks, carry out constabulary duties and act as the eyes, ears and representatives of the Royal Navy wherever they patrol.
Two of the UK's OPVs were recently deployed to Jersey to patrol the waters around the Channel Island.
Among them currently are two generations of River-class ships serving in the Royal Navy, the Batch 1s and the newer Batch 2s.
Operating since the early 2000s, HMS Tyne and HMS Severn belong to the first generation and have largely helped to protect fish stocks.
They have also been frequently called on for general duties at home and abroad.
In 2017, the two ships were joined by a new generation of River-class warships which are larger, faster and more capable.
The River-class vessels are 90.5m long, have a total range of 5,500 nautical miles, a top speed of 24 knots and are capable of carrying a crew of 45 – plus up to 50 Royal Marines.
The vessels also come complete with a DS30B 30mm gun, designed to defend Royal Navy frigates from a variety of missiles, rockets, grenades and explosives.
They also have a GAM BO 20mm gun – a hand-operated mounting carrying an Oerlikon KAA200 automatic cannon.
The newer ships have flight decks designed to operate Merlins, as well as a 16-tonne crane and two Pacific 24 RIBs.
All eight River-class ships are based in and crewed from Portsmouth.