This is the moment a Royal Navy warship collided with a Russian submarine while on patrol in the North Atlantic Ocean:
HMS Northumberland had been searching for the submarine after it disappeared from the ship’s view in the Arctic Circle shortly before the incident took place.
The submarine hit the warship’s sonar - a piece of equipment being towed hundreds of metres behind it - which was fitted with sensitive hydrophones for listening under water.
The incident, which happened in late 2020, was captured by a documentary crew from Channel 5 who were filming a television series called Warship: Life At Sea.
The Ministry of Defence (MoD) has since confirmed the collision between the submarine and the warship, with a UK defence force source telling the BBC that it was not thought to have been deliberate.
Speaking about whether this was a premeditated incident, former frigate captain Commander Tom Sharpe said: “The question is was it deliberate or was it an accident.
“Ship and submarine detection is not an exact science. It could have been a close pass gone wrong.”
The collision reportedly caused damage to HMS Northumberland’s sonar, with the ship returning to a port in Scotland to replace the damaged equipment.
The MoD, which does not usually comment on operations, was forced to do so on this occasion because the incident was caught on camera.
A 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.”
A Navy source reportedly said they believed it was a 'million-to-one chance event', explaining: “The crew of the submarine would have s*** themselves.
“They would have heard a very sudden and unexpected noise like a fork being dragged over a cheese grater."
Foreign Secretary Liz Truss 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."
Rebecca Shepherd