[13] On 6 November 2013, it was announced that the Royal Navy had signed an agreement in principle to build three new offshore patrol vessels based on the River-class design similar to the larger Amazonas-class corvette derivative built at a fixed price of £348 million, including spares and support.

The ships, which were designated Batch 2 of the River class, were to be globally-deployable and capable of carrying out constabulary tasks, such as counter-terrorism, counter-piracy and anti-smuggling.

[19] It was announced on 25 January 2018 that Forth had been accepted by the Ministry of Defence from BAE Systems and would shortly sail to HM Naval Base Portsmouth for commissioning.

[23][24] In October, Anderson Smith, BAE Systems Commercial Director – Naval Ships, admitted that "minor defects" had been found but announced that they had since been fixed.

[27] She then made her inaugural fishery protection patrol and her first visit to an overseas port, which was to Gibraltar before again escorting the same Russian ship through the English Channel.

[28] On 13 January 2020, Forth arrived at the East Cove Military Port in the Falkland Islands on her first operational deployment, taking over from her older half-sister Clyde as the permanently-stationed guardship.