Commander Tom Sharpe, the former frigate captain, told The Telegraph that the “Russian threat to our national undersea communications is real, on our doorstep and ever increasing”. 

“It’s hard to overstate the effect a major disruption of it would cause,” he said, adding that while “forcing the ship to return to port for array repairs would be a significant escalation”, it was “ultimately fruitless because all that happens then is the rest of the team closes in and carries on the mission”. 

While Navy sources insisted there was nothing to suggest the collision was “deliberate”, Cmdr Sharpe cautioned that “it’s unlikely that a T23, even running in silent mode, would be totally invisible to the Russian sub”. 

However, he added it was “perfectly possible that the sub didn’t know exactly where the ship was and in which direction it was heading”.

‘Free world must rise’ to meet Russian threats

News of the incident came as Liz Truss, the Foreign Secretary, told the House of Commons that “the free world must rise” to meet the threats from Russia. 

Moscow has massed 100,000 troops with tanks and missiles batteries in a threat to invade Ukraine.

She told MPs: “Any Russian military incursion would be a massive strategic mistake. Russia is the aggressor here – we urge them to end their malign activity and stick to what they have agreed.

“The only way forward is for Russia to de-escalate and pursue a path of diplomacy. The free world must rise to meet this moment.”

A Ministry of Defence spokesman said: “In late 2020, a Russian submarine being tracked by HMS Northumberland came into contact with her towed array sonar. 

“The Royal Navy regularly tracks foreign ships and submarines in order to ensure the defence of the United Kingdom.”