Dozens of British sailors nearly boiled to death after they were trapped on a broken nuclear submarine returning from a top secret mission.
The mariners were overcome by heat exhaustion when temperatures rose dramatically on board the submarine after a "catastrophic" air-conditioning failure.
Eight submariners were left in a "life-threatening condition" as temperatures on HMS Turbulent passed 60 degrees with 100 per cent humidity.
The previously undisclosed incident in the Indian Ocean has come to light three years later, after the commanding officer at the time gave a dramatic account of the crisis, saying that the situation had been so bad that he thought crew members were going to die.
Ryan Ramsey described to the Plymouth Herald walking around the boat he "saw true fear" in his crew's eyes, "we simply did not know how we were going to get through it," he described.
The vessel had surfaced and Mr Ramsey was on the bridge when engineers told him the air conditioning plants had "catastrophically" failed. As he went below he was met by an "incredible blast of heat," and the first casualties soon began to be taken ill.
The submarine was only three hours from Fujairah in the United Arab Emirates on May 26, 2011, but a decision was made that it was impossible to return to land with a "broken" nuclear submarine because of the political fallout.
Within hours many areas of the 78 metre-submarine had become makeshift sick bays, as 26 crew were taken ill.
"We had casualties in the control room, the engine room, the bridge, the wardroom, cabins, and the toilets and showers. It was absolutely terrifying, and I'm not afraid to say I was scared," he said.
The crew opened two of the hatches to release some of the heat and put some of the casualties outside, but with temperatures on the surface reaching 42 degrees there was little respite. A decision was made to dive to cooler water to reduce the heat.
"It was touch and go before we dived as to what might happen to us and the submarine," Mr Ramsey said.
"We couldn't do anything. I could have radioed for help but it would have taken hours for anyone to reach us. In that time people would have died."
Diving to below 200 metres, the temperatures began to drop and within 24 hours systems had returned to normal and the crew were recovering.