One of Britain's nuclear deterrent submarines has suffered an “unusual” amount of damage as pictures emerge of HMS Vengeance returning from patrol with around 30 per cent of her sonar panels missing.

The ballistic missile submarine returned last week from her latest three-month patrol.

As the nuclear-armed vessel surfaced near the Faslane naval base on the Clyde it was obvious the expected level of wear and tear had been exceeded by up to three times the usual amount.

Britain’s ballistic missile submarines are covered with sonar panels - specially designed acoustic shields to mask any sound from inside the submarine and absorb the sound waves of an active sonar emitted by another vessel looking for the boat.

Any signal bounced off the hull of a submarine coated with the tiles is significantly degraded, thereby reducing the effective range of the sound wave and making it easier for the submarine to hide underwater.

The fin of HMS Vengeance (known as the 'sail' in the US Navy) showing the sonar tiles credit: Dougie Coull Photography

On a typical three-month patrol Britain’s fleet of nuclear-armed submarines, Vengeance, Vanguard, Vigilant and Victorious - collectively known as V-boats - would be expected to shed around 10 per cent of the panels.

Speaking exclusively to the Telegraph a naval source said: “It’s normal for tiles to come off, but to come in after three months looking like that is unusual.

“Nothing’s gone wrong, she’s not been found, but something has happened. She has come back with about 30 per cent of her tiles missing. I’ve not seen one coming back looking like that before.

“Maybe her replacement wasn’t ready, meaning she had a longer patrol, or she had an incident with fishing nets.”

The stern of HMS Vengeance clearly shows a large number of missing sonar tiles credit: Dougie Coull Photography

The Royal Navy's submarine force, known as the Silent Service, has maintained at least one nuclear-armed submarine at sea for 50 years.

Known as Continuous At Sea Deterrence (CASD), the on-duty submarine will leave the Faslane naval base in Scotland with an escorting frigate, then dive to conduct a patrol. The boat will be under the water for three months without surfacing, ready at all times to launch a nuclear strike if ordered to do so.

The boat will patrol at a walking pace and will emit no sound whatsoever in order to remain hidden.

Only a small number of people on board will know where the submarine is at any time and it is not unusual for the crew to place their hands against the outer casing to try to gauge the temperature of the water so as to guess where they might be.

The V-boat fleet started to enter service in the early 1990s with an anticipated life span of 25 years. However, the replacement date has been pushed back a number of times and the next generation of boats carrying Britain’s nuclear deterrent - known as the Dreadnought class - is not expected in service until the 2030s.

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Admiral Lord West, a former First Sea Lord, expressed concern that the four existing boats were being kept in service for too long.

“All of them are being pushed that little bit more so there have to be concerns.

“Am I worried about the extending of life and how long it’s taking to get the Deadnoughts? The answer is yes.

Admiral West criticised the decision in 2010 by the-then Chancellor, George Osborne, to move all costs of the nuclear deterrent submarines into the Ministry of Defence (MoD).

“It’s a political weapon for our ultimate survival; it’s not for fighting wars,” he said.

“The running costs are fine [to come from the MoD budget] because sailors need be trained to do other things as well, but the capital costs should come from central contingency.”

“The Treasury won’t want to do that, but there are a lot of people in the MoD and beyond who feel that would be the right thing to do.”