Royal Navy Begins Trials With Repurposed PSV

A former commercial platform support vessel repurposed by the Royal Fleet Auxiliary has begun sailing under the White Ensign after conversion to a specialist mine‑hunting mothership and a challenging period in service.

Acquired by the UK government from Norway’s Island Offshore in 2023, the vessel began life in 2013 as MV Island Crown, built by Vard. At 317 feet, she worked in offshore oil, gas, and wind support before being adapted at HM Naval Base Devonport for autonomous mine countermeasure duties under RFA management.

Conversion to a mother ship for remotely operated and autonomous systems was completed amid staff and technical setbacks that left the vessel largely idle. 

Reports in August 2024 cited problems with her deck crane, and the ship carried out only a few missions while under RFA control. The vessel was formally commissioned into Royal Navy service in July 2025.

Four months after the handover, Stirling Castle departed Birkenhead for sea trials and training before proceeding to her new base at His Majesty’s Naval Base Portsmouth. 

“Taking Stirling Castle out of lay-up and getting her back into service in just four months has demanded extraordinary things from my team,” said Commanding Officer, Commander Phillip Harper.

The ship’s 55‑strong crew, working alongside RFA personnel, completed extensive maintenance, safety checks and training to ready the platform for trials. 

Over the coming weeks, Stirling Castle will undertake further assessments and operational sea training with embedded autonomous surface and underwater vehicles, after which she is expected to enter full operational service.

When fully operational, Stirling Castle will carry a range of high‑tech autonomous systems intended to transform mine‑countermeasure operations in UK and nearby waters. 

The vessel is part of the Royal Navy’s shift away from traditional single‑ship mine hunting, towards distributed, unmanned systems supported from a mothership platform.

The transfer also follows organisational changes in the Royal Navy’s autonomy programme. A year earlier, the service disbanded its autonomous systems testing team and absorbed its functions into fleet units, bringing development and operational testing closer together.

Stirling Castle will now provide a dedicated afloat test bed and operational base for those capabilities.

The ship currently retains her original blue and white livery, with plans to repaint her grey at a later date to align with Royal Navy colouring. The Ministry of Defence says the conversion and rapid return to sea demonstrate the service’s ability to integrate commercial hulls and cutting‑edge autonomous technology to bolster the Navy’s mine‑warfare capability.
 

Your single solution for technical marine consultancy

Expertise. Innovation. Budgetary value. Global capability. There’s no substitute for experience, which is why Brookes Bell’s Master Mariner services are so sought after.

Our vertically-integrated approach means that we can investigate, troubleshoot and advise on a broad range of maritime matters, whilst providing you with a single point of contact.

Discuss our Master Mariners services today to see how we can support you and your business

For more maritime industry insights, news and information, read the Brookes Bell News and Knowledge Hub…

Wasaline to Launch First Carbon-Neutral Baltic Route | ABB Powers World’s First Hydrogen Fuel-Cell Superyacht | EU Associations Warn Regulatory Hurdles Threaten Subsea Cable Repair