Image copyright Chatham Historic Dockyard Trust

At the height of the Cold War, HMS Ocelot secretly served on the front line. In the clandestine battle against the Soviet navy, she would stay submerged for weeks at a time, silently watching and listening to the enemy. Five members of her crew during the 1960s recall their extraordinary life below the waves.

Brian Defurey, Ron Hitchin, Norman Hart, Richard Dixon and John Wakelin are now all pensioners, but still call each other by the Navy nicknames given to them 50 years ago - Billy, Ted, Nobby, Dixie and Wacker. They often reunite to reminisce about the cramped conditions and camaraderie of working, living and breathing with 65 other men.

"You were always bumping into each other," Billy says. Not that it overly concerned the crew. "Most men on the boat would have considered it just like being in a room inside their house. Besides, any signs of claustrophobia are weeded out very quickly in the Navy."

The daunting training for British submariners - historically denounced by other sailors as "pirates" - included escaping from a deep, underwater chamber without breathing apparatus, and being locked in a submerged, darkened "pressure pot".

Find out more The Russians are coming!, episode two of The Silent War is broadcast on BBC Two on Thursday 12 December at 21:00 GMT Or catch up on BBC iPlayer

But Nobby recalls one rare incident when one man had some kind of panic attack while the Ocelot was dived. "He was shouting 'I want to get out, I want to get out', and tried to open the escape hatch." Overpowered and then sedated - for his own and everyone else's safety - he was looked after until he could be taken off by a passing ship.

If the confinement didn't bother them, the smell was something they did notice.

"The submarine stank," says Dixie. "It stank of diesel, sweat, fags and food. Water was rationed, particularly if you were going on a sneaky [a spying operation] because you didn't know how long you'd be gone for. There was only a small bowlful a week to wash and shave in. So no-one bothered."

Even worse, on long patrols, bags of rubbish built up and festered in the gangways. "It couldn't be got off the boat as it would give away our position to the enemy", explains Billy. "So it stayed there until we could dispose of it safely."

The crew could wear what they wanted once the boat had put to sea. Known as "pirate rig" this was often just a pair of old jeans or shorts and a top, which were rarely changed. Billy recalls Dixie's socks would "stick to the wall" if thrown. He's also alleged to have worn a teddy boy suit and brothel creepers, although Dixie denies this.

Media playback is unsupported on your device Media caption Footage from HM Submarine Ocelot

The Ocelot's full service records have never been released by the Ministry of Defence but in the 1960s it was heavily involved in clandestine operations, along with Nato exercises and weapons testing. Most operations were never revealed, even to the crew, who were generally told they were executing a training exercise or "war game".

"You knew you were about to go off on a real sneaky, though," says Nobby, "because someone would paint out the numbers on the conning tower."

One of the "exercises" involved the boat sitting undetected on the bottom of the sea, quietly gathering information on an enemy ship above. The men followed a "silent routine", as the enemy sonar operator would have literally been able to hear a spanner drop on the Ocelot. Communicating in whispers, they also put rubber mats on the floor and crept about in rubber-soled shoes.

HM Submarine Ocelot Image copyright Chatham Historic Dockyard Trust Launched in 1962, she served throughout the Cold War

A diesel-electric submarine, the Ocelot carried homing torpedoes and about 70 men

One of the quietest boats of her time, she was highly effective at surveillance and intelligence gathering

Leaving active service in 1991, she's now a visitor attraction at Chatham Dockyard Source: Historic Dockyard, Chatham

Often the crew had no idea where they were, although the temperature on board might suggest the Mediterranean or freezing Russian waters. When they joined up, the men recall signing the Official Secrets Act and being forbidden to talk about their job.

On board, every man had his own job to do, whether it was loading torpedoes or operating radar, but all had to have a working knowledge of the boat. At night it was lit by dim, red lighting. There were three alternating watches or shifts, and each day was split into working, watch keeping, cleaning, sleeping and eating.

"Food was better than general service [surface ships]," remembers Wacker, "I never had a bad dinner." "Babies' heads" (steak and kidney puddings) and "train smash" (tinned tomatoes and bacon) and other tastefully named meals were cooked by a chef in the galley.

They ate in the cramped surroundings of the mess deck while the officers ate in the wardroom. Fresh supplies lasted around two or three weeks after leaving harbour, and then everything came out of tins.

Besides tea and coffee, the day's liquid intake included the famous Navy rum ration. Stopped in 1970, most of the Ocelot boys fully enjoyed the high-proof spirit served at "tot-time". Billy remembers the wave of excitement when "up spirits" was announced. "The rum was like honey - everyone would cheer."

Image copyright Other Image caption Tot time: Ted (back, second left) and Billy (back right)

Off-duty, the men worked hard to distract themselves in the absence of TVs and music. Card and board games were popular, and many read books - a lot. Football results were anxiously waited for.

Conversation always stayed general and light-hearted - no-one discussed operations, religion or politics, knowing they'd be on dangerous ground. The men simply had to tolerate each other, and while tempers could naturally fray, especially towards the end of long patrols, disputes were rapidly quelled for everyone's safety.

Take a submarine tour Image copyright National Maritime Museum Watch a slideshow about these amazing underwater warships on Your Paintings

Wacker recalls quizzes being piped through the boat and also attending Sunday "church" services in the fore-ends. Taken by an officer, the hymn For Those in Peril on the Sea was often sung by a congregation squashed in next to the torpedoes.

The mess deck was also the sleeping area, games room and cinema. Film reels were loaned by the Navy library in harbour - Tom And Jerry was extremely popular ("the Fred Quimby ones," notes Wacker), as was The Magnificent Seven.

"Everyone would take a part, Steve McQueen or whoever, and then we'd turn down the sound and re-enact the lines," laughs Nobby. They'd be watched one after another, even backwards and in fancy dress while others were sleeping in the bunks behind the screen.

The bunks were so small that once in, you couldn't turn over. Dixie remembers his feet permanently sticking out of the bottom. Every man was issued with his own sleeping bag and pillow, but the bunks were often "hot bunks" - one man out, another man in. "You were so tired, you just dived straight in, clothes and all," he recalls.

Like some, Wacker had a photo of his wife and daughter pinned up by his bunk. Others weren't so romantic. One had a picture of the highly desirable Aston Martin DB5 - the Bond car in Goldfinger - in his radar office.

Image copyright John Wakelin Image caption John "Wacker" Wakelin (left) on HM Submarine Tiptoe

Did they miss their wives and girlfriends? Nobby confesses it became more difficult towards the end of his time on the boat, and Wacker, like many others, came out after children began to appear on the scene.

The 'Queen's pirates' Image copyright Royal Navy Submarine warfare was initially considered "un-gentlemanly", and led to comparisons with pirates

Royal Navy submarines returning from action still fly the Jolly Roger

The "silent service" has been involved in every significant operation since 1902

The Victoria Cross has been awarded to submariners seven times Source: Royal Navy

The men felt the job had to be got on with, and the total isolation - no phones, no telegrams, no mail - just had to be dealt with. Personal telegram messages could be received by the boat but only when near or on the surface, and often these were withheld if an operation was ongoing.

As a radio operator, Nobby received the signals, and sometimes it wasn't good news. "We got quite a few 'Dear Johns'," he said, "but the worst signal I ever received came through for a friend whose wife had miscarried. The captain ordered me not to tell him until the end of the operation, knowing how upset he'd be." Once in harbour, the man was told, and was taken off the boat. "He was in tears. I never saw him again."

Those who volunteered to serve knew conditions would be primitive and very dangerous. What made them do it?

One big draw was the unique camaraderie of submariners, in part generated by the smaller division between officers and ratings and the more lenient discipline and uniform compared with general service.

But for many of these young men it was the "operational reward" - a rare chance in the Cold War to go head-to-head with the enemy, and in a world-class warship. Or, as Wacker puts it, "it was a bit of a Boy's Own adventure".

Image copyright Brian Defurey Image caption Billy (left), Dixie (centre), Ted (third right) and Nobby (second right) with crewmates in 2012 at the 50th anniversary of the Ocelot's launch

The Ocelot boys regularly reunite to recall their remarkable days of bravery under the seas. While the navy tattoos have blurred with age, the camaraderie is still clear.

"You don't make friendships like this on Civvy Street," says Billy.

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