The UK Royal Navy (RN) has commissioned a former offshore support vessel (OSV) into the front-line fleet to accelerate Mine Hunting Capability (MHC) Block 1 operational development and integration.
Previously operated by the Royal Fleet Auxiliary (RFA) as RFA Stirling Castle, the ship was commissioned as HMS Stirling Castle in a 21 July ceremony in Birkenhead. Following the hoisting of the White Ensign, the 45-strong ship’s company moved on board the ship.
Stirling Castle is a UT 776 CD type OSV originally delivered by Vard Brevik in 2013. The ship – previously named MV Island Crown – was acquired from the commercial market for £39.8 million at the start of 2023 to provide a UK host platform for autonomous MCM payloads procured through the MHC Block 1 programme. The vessel subsequently underwent modification at Devonport for its new role, and began sea trials and training under its new name in late May 2023.
While Stirling Castle performed some limited trials as part of the RFA fleet, the vessel has been effectively sidelined since mid-2024. This situation, largely attributable to the RFA’s acute manpower pressures, resulted in the ship being laid up at Cammell Laird’s Birkenhead shipyard late last year.
The transfer of an RFA ship to the RN is highly unusual, but reflects the importance attached to pushing the MHC programme forward. In a statement, the RN said that Stirling Castle “has been designated a warship as she will be committed 100% of her time to front-line operations, allowing Royal Fleet Auxiliary personnel to focus on their primary task of crewing the array of tankers and support ships across their fleet”.
It added: “Stirling Castle…will now take her place on front-line duties, carrying high-tech equipment, including autonomous surface and underwater vehicles, for specialist mine hunting operations, primarily in UK waters.” The vessel will initially retain its unique blue and white livery as a commissioned ship, although there are future plans for a repaint in standard RN grey.
HMS Stirling Castle will be base ported at HM Naval Base Portsmouth. Work to regenerate the ship has now begun at Cammell Laird, with the intent to have the ship back at sea later in 2025. Operations with MHC Block 1 autonomous minehunting and sweep systems operated by the RN’s Mine and Threat Exploitation Group (MXTG) should follow by early 2026.
Growing integration experience with Stirling Castle and the mission systems delivered to the MHC Block 1 is seen as a priority as it will inform and influence requirements for the OSV competition planned to run as part of MHC Block 2. Requirements call for the procurement of three ‘mother ship’ OSVs – likely based on a commercial derivative design – to support deployed mine countermeasures (MCM) operations. Delivery is set for the early 2030s.
An RN source close to the MHC programme previously told Naval News that the objective was for the OSV to be a less complex vessel, thereby allowing greater investment to be made in the MHC mission systems and associated payloads. There was also a desire to ensure that the configuration of the OSV would not constrain future MHC mission system options to a certain size/length, nor foreclose the opportunity to embark other vehicles/payloads outside of the MCM role.
