The first of the new Royal Navy undersea surveillance ships has arrived in Cammell Laird, Birkenhead, and is set to strengthen the UK's critical subsea infrastructure.
Following a formal handover to the Royal Navy in the coming days, the ship will undergo a period of military modifications.
The vessel, currently named Topaz Tangaroa, is due to be operational in the summer.
The 98m-long, adaptable offshore patrol vessel will act as a 'mother ship', and will operate remote and autonomous offboard systems for underwater surveillance and seabed warfare.
Defence Secretary Ben Wallace said: "The first of two dedicated subsea surveillance ships will join the fleet this summer, bolstering our capabilities and security against threats posed now and into the future.
"It is paramount at a time when we face Putin's illegal invasion of Ukraine, that we prioritise capabilities that will protect our critical national infrastructure."
The ship is to be repainted, renamed and have important military equipment installed, before taking up its role as the first of two Multi-Role Ocean Surveillance (MROS) ships, operated by the Royal Fleet Auxiliary (RFA).
The 6,000-tonne vessel is equipped with a helipad, crane, an expansive working deck and features a 'moon pool' – a large access point in the underside of the hull through which submersible capabilities can be launched.
Commodore David Eagles, head of the Royal Fleet Auxiliary, said: "This is an entirely new mission for the Royal Fleet Auxiliary – and one we relish.
"We have been entrusted with supporting a key operation to safeguard the UK's infrastructure, security, and prosperity and that fills all of us in the RFA with pride.
"These are really exciting times."
The vessel was selected to meet the requirements of the Royal Navy, having been built four years ago to support a mix of underwater operations, including work on oil rigs, construction, maintenance and inspection work, as well as autonomous submarine operations.
It will be crewed by about 24 RFA sailors, with 60 Royal Navy specialists operating the undersea surveillance systems and other survey and warfare systems when embarked.
DE&S Director General Ships Vice Admiral Paul Marshall said: "DE&S (Defence Equipment & Support) worked at pace to successfully accelerate the purchase and delivery of the first ship under the critical MROS programme.
"We continue to work with agility to support the UK Ministry of Defence in addressing both the current and future threats posed by an ever-changing world."
The programme for the acquisition of a second ship is currently in its concept phase.