Why the Type 31 frigate suits a modern navy

At Babcock’s yard in Rosyth, work is now under way on several Type 31 frigates at the same time. The lead ship, HMS Venturer, was launched in June 2025 and is being fitted out, the second, HMS Active, was floated off in March, and the remaining three of the five are taking shape behind them.

The Type 31, formally the Inspiration class, has drawn relatively little public attention, and the ship was always intended as a steady, practical addition to a fleet that is short of hulls.

The design itself is a deliberately cautious choice, because the ship is based on Babcock’s Arrowhead 140, which grew out of the Danish Iver Huitfeldt class and has been in service at sea for well over a decade, so the Navy is buying a hull that is already understood and proven, which lowers the risk that has dogged some recent British programmes. At close to 140 metres and around 5,700 tonnes the Type 31 is a large frigate, and it has been designed to run with a core crew of only about a hundred, with space for around 190 once specialists and aircrew are embarked.

A large hull worked by a small crew leaves a good deal of room and weight to spare, and on a warship meant to serve for thirty years that spare capacity matters, because it has to be able to take on equipment and whole roles that no one has foreseen. The Type 31 has a sizeable mission bay that holds payloads in standard shipping containers, a flight deck and hangar for a Merlin or Wildcat, and boat bays built for uncrewed craft as well as ordinary sea boats, so a single ship can be fitted out for anti-submarine work, mine clearance, maritime security or disaster relief and then changed over again when the job changes.

On commissioning the ships will carry a fairly light armament for their size, with a 57mm Bofors gun, two 40mm guns and the Sea Ceptor air defence system, and that has drawn criticism from some observers. The Navy’s answer rests on the same spare capacity, because the design was always meant to be filled out later, and a planned capability insertion will add a 32-cell Mark 41 launcher able to fire Tomahawk cruise missiles, if ordered, taking a general purpose frigate to something considerably more potent over the life of the ship.

That same flexibility is why the Type 31 fits the direction the Navy is now taking. The First Sea Lord, General Sir Gwyn Jenkins, has put a so-called Hybrid Navy at the centre of his plans, a dispersed and digitally linked force in which crewed warships work with drones and uncrewed vessels, allowing the fleet to cover more sea without manning more ships.

The force such a navy needs is already being assembled, because through an initiative it calls ARMOR Force, Babcock has teamed with the American shipbuilder HII to bring its ROMULUS family of AI-enabled uncrewed surface vessels into British service, and the firm has put ROMULUS forward as the basis for the Royal Navy’s first autonomous escort, with the aim of having one in testing around 2027. The vessels run on a mature autonomy system that HII already uses across American and allied programmes, and HII has expanded a site at Portchester in Hampshire to support them. A crewed frigate with the room, the deck space and the boat bays to act as a command ship for vessels like these is the kind of ship the plan needs, and the Type 31 was built with that in mind.

The thinking behind all this was set out in the 2025 Strategic Defence Review and owes a great deal to what Ukraine has done to the Russian fleet in the Black Sea, where cheap uncrewed boats have inflicted serious damage on a much larger navy. The role in mind runs from hunting submarines to standing watch in the North Atlantic and the High North.

Other navies have been buying the design, which is some measure of its quality. Sold for export as the Arrowhead 140, it has been picked by Poland for its Miecznik programme and by Indonesia, where the first locally built ship took to the water in December 2025. Denmark is considering an order put at around a billion pounds, Sweden has shown interest, and the United States has taken a licence. Babcock’s marine chief, Sir Nick Hine, talks of getting to “31 by 31”, roughly 31 of the ships built or ordered around the world by 2031, and each sale spreads the development cost, sustains several thousand skilled jobs at Rosyth, and leaves friendly navies operating a common hull that is easier to work alongside at sea.

The cost of the programme is widely misread, it should be noted that the figure of about £250m a ship, or £1.25bn for the five, pays for the bare platform, because the radar, combat system and weapons are funded separately by the Ministry of Defence as government furnished equipment, so the real cost of each ship is higher once that kit and the supporting shore facilities are counted, which is simply how the Ministry chooses to split the budget for a warship and not a sign of a hidden overspend.

Costs have risen during the build as well, with ministers acknowledging an extra £40m from the pandemic and supply problems, Babcock taking a £90m loss on the contract in 2024, and the company booking a further £140m charge this May for higher than expected rework and for work done out of sequence on the first ships. Much of that rework came from changing the design to build in the later upgrades, the ships further down the line have been far less affected, and figures of this kind are normal for the first vessels of a new class, so the red delivery confidence rating the programme carries reflects a demanding early stage of build and not a project that has gone wrong.

The lead ship is expected in service towards the end of the decade, and the rest of the class should follow in the early 2030s.

The Royal Navy is getting a large and adaptable frigate built on a proven hull, with the space and power to grow into a much more heavily armed warship and to serve as the crewed hub of the uncrewed force the fleet is now assembling. It arrives at a time when the Type 23s are ageing and there are too few escorts to go round, so hulls that can be delivered in numbers and turned to many different tasks are worth a great deal.

With allied navies choosing the same design and the wider hybrid fleet taking shape around it, the Type 31 stands as a sensible and well-judged answer to the demands the Navy actually faces in the years ahead.