How two British engineers were trapped in a tiny stranded submarine 1,500ft below the Atlantic... with just hours of oxygen left: New book plunges YOU into the heart of one of the most terrifying undersea dramas ever

 When Roger Mallinson glimpsed a human face, framed by ‘flaming blond hair’, through the porthole of his mini-submarine, his first delirious thought was ‘Is that a mermaid?’

A split-second later, he understood. The face belonged to a diver, bringing a slim hope that he and his co-pilot Roger Chapman might be rescued. 

But as their tiny capsule rocked and lurched helplessly, hundreds of feet below the surface of the Atlantic, Mallinson realised it was proving impossible for the diver to fix a cable to haul them up.

Another rescue attempt had failed. And their air supply was almost exhausted.

Inside the steel can, Mallinson and Chapman were bruised, battered, racked with pain and starved of oxygen. For three days they had been trapped in a claustrophobic nightmare. It was August 1973, and the world watched and prayed.

Now the end was close. If their Vickers submersible was not pulled up from the depths within the next few hours, the two men were certain to suffocate.

There was nothing they could do, except wait — and try to control their terror.

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When the sub hit bottom and turned to bury its nose in the seabed, the men were hurled against the walls and then tumbled over each other. As they gathered their senses and found a torch, they saw the depth gauge read 1,575ft

The irony was that the dive — the 325th of a mission to embed communication cables in the ocean floor — was almost finished and had been going well before the unthinkable happened.

Both men were tired and quiet as the sub bobbed to the surface. Soaked in sweat from the humidity, they were hungry too. A towline was attached, winching them in to the mother ship, Voyager.

Suddenly, water alarms began to shriek. Neither pilot was too worried: it was common for condensation to get into the filters and trigger an alert. But then the Pisces III wallowed backwards, and the portholes turned dark as they started to sink.

They did not know it yet, but a damaged hatch cover — which Mallinson had earlier flagged for repairs, only to have the request overruled by his bosses — had sprung open when, in a freak accident, a tow rope had wrapped around a hatch bolt. Tons of water rushed in.

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Even when the Pisces III reached the surface, would it be possible to open the cabin hatch? It was badly damaged, and there was every chance it was jammed. The rescue team tried to force the bolts securing the hatch, as Mallinson and Chapman, still trapped inside, hammered on it with their fists. The two men are seen emerging after the world’s deepest rescue

‘Look at the bloody depth gauge,’ Chapman shouted. The needle was moving fast, to 100ft and then 150ft.

At 175ft, the descent of the Pisces III came to a juddering halt. Both men stumbled against the steel casing. The sub was hanging nose down, suspended by the towline. 

As the currents caught it, the vessel began to shake and sway violently ‘like a rat in a terrier’s mouth’.

On board the Voyager above, an emergency diver got ready to go down and attach a second, stronger line. It was a difficult, dangerous plan but there seemed no alternative.

Inside the sub, the pilots faced other serious problems. A spare battery for the underwater telephone, the size of a breeze block, had come loose and was crashing from one side to the other. A sonar set had also broken free and was battering both men.

Seizing a spanner, Mallinson struggled to find a footing as he tried to undo the floor bolt that secured the 400lb lead block beneath the sub that gave it extra ballast — weight designed to help it hug the ocean floor.

Extra weight was the last thing they needed now. But as Mallinson worked the bolt loose, a tremendous bang shook the Pisces III. The towline had snapped.

Freed from its last restraint, the sub turned end over end in the water until it was sinking stern-first. The pilots raced to secure every loose object, anything that could ricochet around the cabin when they hit bottom, then switched off all the electrical equipment, to minimise the risk of an explosive fire on impact.

As the gauge span past 1,000ft and then 1,200ft, Chapman stacked seat cushions across the back of the cabin, to soften the impact.

Mallinson shouted: ‘Bite on a rag,’ and they stuffed cloths in their mouths to prevent themselves from biting through their tongues on impact.

When the sub hit bottom and turned to bury its nose in the seabed, the men were hurled against the walls and then tumbled over each other. As they gathered their senses and found a torch, they saw the depth gauge read 1,575ft.

They were trapped at a depth twice that of any previous submarine rescue. There was more than enough water above them to submerge the Empire State Building.

Chapman and Mallinson waited in silence, barely daring to breathe, for fear that the sub was lying on an outcrop of the Continental Shelf. If they started to fall again, into a chasm, they might not stop for a mile or more.

Their first thought was oxygen. In theory, the full tank should last for 30 hours. By lying still and breathing as slowly as possible, they might extend it to three days.

But the theory would be useless if they could not also operate the ‘scrubber’, a filter that cleaned the air of carbon dioxide that their lungs continually breathed out. If that didn’t work, they would die.

Mallinson thought back to the previous 24 hours. He had been feeling sick for days (the result of food poisoning from a meat and potato pie at a pub, his last meal on leave) but despite that had worked all night repairing damage to the sub’s manipulator — its robot arm, used for working with tools and holding the cable.

An expert engineer, he had helped to restore the sub, the Pisces III, after it was bought second-hand and in poor condition. No one in the world knew more about the mechanics of this vessel.

But the 35-year-old father-of-three had more worries than just the manipulator. The ‘aft sphere hatch’ — the lid at the back — was not operating as originally designed and needed repair. 

When Mallinson told his boss about his concerns, he was told brusquely to ignore the problem. The hatch was a cover at the back of the sub, something like the boot on a saloon car.

It gave access to the storage bay, where equipment was stored. It couldn’t be opened underwater, and it didn’t open onto the main cabin. But keeping it watertight was essential.

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Divers are pictured opening the minisub’s hatch. Their cabin was just 6ft across. To see out of the porthole and operate the manipulator, they had to bend double, with their heads on their knees, or lie flat out

Reluctantly, Mallinson agreed to make the dive without insisting on repairs. However, instinct made him replace a half-used oxygen canister with a full one.

Company protocol said half a tank, with additional oxygen onboard, was all the two-man sub needed for eight hours of operation. Canisters should not be discarded half-full. Mallinson ignored the protocol and made the switch without permission.

As the 12-ton sub was winched into the water from the Voyager, they were a similar distance from the southern tip of Ireland and the north coast of Brittany, about 150 miles south-west of Cork.

Their job was to secure the Post Office’s transatlantic telephone cable, burying it into the seabed so that it could not become entangled in trawler nets. The work was difficult: Mallinson described it as like driving down the motorway in thick fog and trying to follow a white line.

Their cabin was just 6ft across. To see out of the porthole and operate the manipulator, they had to bend double, with their heads on their knees, or lie flat out.

There was no toilet.

Almost the only light relief was provided by dolphins. The previous day, when Mallinson was in the communications room aboard the Voyager, messages to the underwater telephone on another sub were interrupted by dolphin squeaks and chatter. It was something he welcomed.

When a crew member stuck his head around the door and said a large pod was off the bow, Mallinson asked him to mind the comms while he fetched his cine camera and went up on deck.

‘I’ve never seen anything like it,’ he said. ‘The whole sea as far as you could see, horizon to horizon, was dolphins.’ But by the time he’d got the camera out of its case, all he caught on film were six tails, disappearing under the water.

Now, facing every submariner’s ultimate nightmare, Mallinson and Chapman needed to test the scrubber — the machine that removed the carbon dioxide that, if it stayed, would kill them.

It worked. There were two clockwork timers with plastic dials that they used to trigger an alarm every 30 minutes to prompt them to activate the scrubber. If they fell asleep and failed to switch it on, there was a good chance neither of them would wake up.

The true terror of their situation made itself felt. Chapman was trembling with fear and cold.

Escape was impossible. The weight of water meant the hatch could not be opened at this depth but if it could, their bodies would be crushed by the 50-ton pressure.

Chapman made an inventory of their supplies. Only one soggy sandwich was left — Mallinson took jam, Chapman, a 28-year-old former Royal Navy submariner, preferred cheese and chutney.

Apart from that there was a can of lemonade, half a flask of black coffee, a tin of powdered milk, a packet of sugar, two apples — plus three biscuits and the standard lifeboat ration of glucose tablets. The temperature inside their underwater prison was 10c but with 95 per cent humidity and condensation running down the walls, it felt much colder.

The underwater radio telephone was working. A message from the surface reached them: the Voyager was heading back to Ireland, to fetch help . . . help that was at least 30 hours away. Until then, the trapped men must simply cling to life and wait.

Other ships joined the rescue mission, including the Royal Navy’s survey ship HMS Hecate, a Canadian coastguard vessel, and a U.S. navy submersible designed for finding unexploded bombs.

News of the crisis spread quickly. At 1.30am on Thursday morning, 16 hours after the sub sank, the underwater phone jangled to life. The line was crackly but both men heard the message: ‘Best wishes to Pisces crew and hope all goes well, from Queen Elizabeth.’

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Reunited: Roger Chapman (left) and Roger Mallinson with their wives after the rescue

Both men were moved by HM’s thoughts. Only much later did they realise the message was from the transatlantic luxury liner QE2.

Mallinson felt a rising anxiety for his wife Pamela and their three children, who would be left fatherless if he did not survive. He knew Chapman was recently married, to June, and had yet to start a family.

He didn’t know whether this was a source of relief or regret to his companion but, in a very British way, he thought it better not to ask. Emotions, like blood, could go everywhere when spilled.

To distract himself, Mallinson — a keen musician — imagined Bach’s organ music in his head, sometimes moving his fingers as if to mimic a keyboard. It was almost the only movement either man allowed himself. They knew that by remaining motionless and taking shallow breaths, they could reduce their oxygen intake.

They also began experimenting with the CO2 scrubber, leaving longer intervals between cycles. This meant the air they were breathing was thinner, eking out their oxygen supplies. But it also meant they began to experience aches and blinding headaches.

Mallinson had another worry. His stomach, still unsettled from the pub’s meat pie, was racked with cramps. With no toilet, he used a plastic bag and knotted it.

The stench made the stuffy conditions worse still. The curved walls dripped with condensed vapour from their breath, and when a drop of water splashed on Chapman’s face his first thought, close to panic, was that the outer shell was starting to leak.

To combat the cold, the men huddled together, spooning as mountain rescue teams do to combat hypothermia. When they could snatch sleep, it was only for a few minutes. Mallinson’s pounding headache was getting worse, not helped by the way he had to lie with his feet higher than his head.

Both were getting desperately thirsty. With no water, all they could do was lick condensation from their fingers.

Over the long hours that followed, messages came over the phone that a sister miniature submarine was making repeated efforts to find them. Frequently the phone link was inaudible, drowned out by clicks and rattles. It was the sound of dolphins.

Chapman found the interference frustrating, but Mallinson was strangely comforted. It was as if the dolphins were trying to reassure them, he thought.

To aid their sister submarine, the men tried chanting, in the hope that on the silence of the seabed their voices might be heard: ‘Here we are, here we are, somewhere near the cable, must be near the pinger, depth is 1,575 feet, come and find us, come and find us.’

The pinger was a device on the transatlantic phone cable. They knew it was close by because it was so loud.

By early on Friday afternoon, when the men had been stranded for more than 50 hours, the sister sub Pisces V located them. They celebrated by cracking open the can of lemonade.

But multiple attempts to secure a rescue line failed. One submersible sprang its own leak and had to return to the surface. Another developed an electrical fault. Once, a hook and line simply refused to work, and could not be attached.

Finally, in the small hours of Saturday morning, nearly 70 hours into the ordeal, two lines were secured, the first by a Vickers manned submersible and the second by the Americans using a remote controlled vehicle. The most terrifying part of the rescue was just beginning.As the sub lurched upwards, both men were hurled against the bulkhead. The plastic bag that had been their portable toilet burst. With the metal sphere jolting and spinning, they were helpless, thrown about in what Chapman called, ‘a crazy upside-down world of noise, foul smell and fear’.

The greatest of those fears was that the rescue line would snap and the sub would fall again.

The ascent had to be halted twice — the first time because one of the other subs was entangled in the rescue line, the second time to attach another, stronger rope.

Even when the Pisces III reached the surface, would it be possible to open the cabin hatch? It was badly damaged, and there was every chance it was jammed.

The rescue team tried to force the bolts securing the hatch, as Mallinson and Chapman, still trapped inside, hammered on it with their fists.

At last, with a tremendous bang, the lid slammed open. At that point, British to the last, the two men had their only argument of the entire, catastrophic episode — each insisting the other should be first through the hatch to safety.

Later, when the cylinder was examined, they discovered how close they really came to suffocation. There was enough oxygen left for just 12 more minutes.

Roger Chapman went on to pioneer the use of unmanned submarines, and was an adviser to the team that tried to rescue the crew of the stricken Russian Kursk nuclear submarine in 2000. He avoided using lifts after the Pisces accident. He died last year, aged 74, from cancer.

Roger Mallinson continued to work in Vickers submersibles for five more years. He is now a keen restorer of classic cars and steam engines. Until Chapman’s death, the two men met every year at the anniversary of the Pisces accident, to enjoy a pint together.

Adapted from The Dive: The Untold Story Of The World’s Deepest Submarine Rescue, by Stephen McGinty, to be published by HarperCollins on June 10 at £16.99. © Stephen McGinty 2021. 

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