Duke-class (Type 23)

The Type 23 frigate, also known as the Duke class, was conceived in the late 1970s as a light anti-submarine vessel intended to counter Soviet nuclear submarines in the North Atlantic. Replacing the Leander and Type 21 classes, the design was announced in the 1981 Defence White Paper as a simpler alternative to the Type 22. Experience from the Falklands War led to design revisions that integrated anti-air and anti-surface capabilities, transforming the class into general-purpose warships. HMS Norfolk, the lead ship, entered service in 1989.

The class utilizes combined diesel-electric and gas (CODLAG) propulsion, which allows for quiet running during anti-submarine operations. The design incorporates radar cross-section reduction measures and automation to reduce crew requirements. Primary sensors include the Artisan 3D radar and, on specialized anti-submarine variants, the Sonar 2087 towed array. For anti-air defense, ships have been refitted with the Sea Ceptor vertical launching system, replacing the original Sea Wolf missiles. Anti-ship capabilities are transitioning from Harpoon missiles to the Naval Strike Missile. The vessels are equipped with a Mark 8 naval gun, automated small caliber guns, and Sting Ray torpedoes. Aviation facilities support the embarkation of Wildcat or Merlin helicopters and uncrewed aerial vehicles.

Sixteen vessels were completed by Yarrow Shipbuilders and Swan Hunter. The class formed the core of the Royal Navy's frigate force for three decades. Between 2006 and 2008, the Royal Navy transferred three vessels—the former Norfolk, Marlborough, and Grafton—to the Chilean Navy, where they remain in active service. Operational history includes naval gunfire support during the 2003 Al Faw assault in Iraq and the 2011 destruction of gun batteries in Libya. In March 2024, the Sea Ceptor system was used operationally for the first time by HMS Richmond to intercept attack drones. Retirements since 2021 have reduced the Royal Navy to five Type 23s — Somerset, Sutherland, Kent, Portland and St Albans — its smallest frigate force on record: HMS Northumberland paid off in March 2025, HMS Lancaster in December 2025, and the withdrawal of HMS Richmond and HMS Iron Duke was announced in July 2026. The remainder are to be replaced by the Type 26 Global Combat Ship and Type 31 frigate.