Type 23 Duke class

The Type 23 frigate, also known as the Duke class, was developed for the Royal Navy during the late 1970s and 1980s to counter Soviet submarines in the North Atlantic. Entering service from 1989, the class was designed around quiet propulsion, advanced sonar systems, and an embarked helicopter, making anti-submarine warfare its primary role. Over time, the ships were upgraded with modern radar, air-defense missiles, and land-attack capabilities, allowing them to perform a wide range of missions including escort duties, maritime security, counter-piracy, humanitarian operations, and multinational naval deployments. Several Type 23 frigates have also been exported or are being transferred to allied navies as they are gradually replaced in Royal Navy service by the newer Type 26 frigate and Type 31 frigate.

By 2013, these members of the Type 23 Fleet had been converted for Merlin operations: Kent, Lancaster, Monmouth, Northumberland, Richmond, Somerset, St Albans, Sutherland, Westminster.

Although now that the Merlin HM.2 conversion programme is underway, the UK has so few front line Merlin airframes, that Lynx (example) are being recycled to make up the numbers.