THREE of the four Royal Navy Faslane-based Vanguard submarines are at sea in a deployment that is regarded by some experts as unusual.
At least one of the three vessels is understood to be carrying nuclear-armed ballistic missiles.
One submarine is always maintaining Continuous At-Sea Deterrent (CASD) patrol, with others coming on stream as appropriate to relieve the single boat operation and take up the charge.
To have three at sea at the one time is unusual but not unprecedented. It last occurred in 2022.
Naval observers say the most significant aspect of this current movement is more likely to be signalling the return of a third boat to the operational rotation.
Vanguard availability in recent years to be part of the CASD patrol has effectively depended on two submarines alternating patrols.
This has led to longer deployments, including a record 205-day patrol completed in April this year.
Each of the previous nine patrols had exceeded five months. Restoring three boats to the rotation would give considerably more room for maintenance, training and crew recovery and could allow patrol lengths to begin falling towards more sustainable levels.
Defence correspondent Tom Sharpe, who spent 25 years in the Royal Navy commanding four warships, said: “If this means the operational availability of those boats is going up then this is a good thing.
“This isn’t anything indicative or sinister, just routine operational scheduling.”
The UK Government maintains deliberate ambiguity about the detailed readiness and loading of its defence deterrent, so it cannot be stated that additional Vanguard boats could never be used to increase readiness during a crisis.
Experts say three boats being at sea does not necessarily mean Britain has three nuclear deterrent patrols underway.
A Ministry of Defence spokesman said: “Our nuclear deterrent is the cornerstone of our national security, protecting the UK and our NATO allies every moment of every day.
“We remain the only European ally to commit its nuclear deterrent to the defence of NATO. This means that all NATO Allies already benefit from the protection of our nuclear deterrent.
