Outside the Diving Museum in Gosport it looks like a Doctor Who props yard. A variety of weird and wonderful suits and contraptions are on display, but to one the museum’s curators, John Bevan, one yellow pod has a personal attachment.
From March 3-18, 1970, this compression chamber was John’s home when he participated in a controlled experiment – a simulated dive to more than 1,500ft, shattering records of the time.
John opens the hatch on the tubular construction and we peer inside. It has tiny portholes and is barely tall enough to stand in, but to the 70-year-old, originally from Llanelli in Wales, it was a lot of fun.
‘It was like a camping holiday in a caravan with three meals a day provided. Great,’ he says.
John lives with his wife Ann at Alverstoke, just down the road from the museum and even closer to the old buildings of the Royal Naval Physiological Laboratory where the experiment took place.
After studying at the Portsmouth College of Technology, John was working as a scientist there when he and his colleague Peter Sharphouse were selected for the task.
‘While I was there the lab started a long-term project to find the maximum depth a human being could descend to. To do that we acquired a new compression chamber which had a depth capability of 650 metres,’ says John.
‘The first stage of this project was to “dive” to 1,500ft, or around 450 metres.
‘The reason we chose that depth was that we knew it would break through a thing called the helium barrier, known internationally as the limit of human depth capability.
‘It was set at about 1,200ft, because the Americans had attempted a dive at this depth but had to abort because the two subjects in the chamber were showing signs of going into convulsions – shaking and twitching – and going into micro sleep, slipping in and out of consciousness.
‘We thought we could beat that depth and we were successful.’
The secret of their success was that their simulated descent was staggered, spending a day at 600, 1,000 and 1,300ft with other hour-long breaks in between and finally staying at 1,500ft for 10 hours.
‘When we stopped at all these points for a day it gave the body time to acclimatise,’ says John.
‘We were running all these experiments while we were in there including taking blood samples and carrying out balance and coordination tests. We were guinea pigs.’
John couldn’t feel the pressure, so to speak, but it was evident through various side effects.
‘If you moved your hand side to side you could feel the resistance, but it was less dense than being in water.
‘What you did notice was that if you turned a page it wouldn’t flip but bend.
‘You also couldn’t breathe through your nose. It was like breathing through a straw.’
Certain foods and objects were off limits because of the conditions.
‘We had some boiled sweets while we were down there,’ adds John.
‘In a boiled sweet there are usually little bubbles of air, and these are at a normal pressure.
‘As you were sucking them the wall of the sweet would wear down and then the bubble imploded and your tongue got sucked into the hole.
‘It was quite painful so boiled sweets became a no no.
‘There was a food lock through which we got our meals, which would be adjusted to our pressure so we could open the hatch.
‘If you put a polystyrene cup in there it would shrink to a tiny size. Sometimes we put them in there for fun.’
Regular air was unsafe to breathe under pressure so John and Peter had to breathe a gas which was 99 per cent helium and one per cent oxygen.
‘Nitrogen, which is in the air we breathe, becomes a narcotic at depth, so if we had inhaled that we would have got drunk and quickly became unconscious,’ says John.
‘Helium is a very thin gas so it was easy to inhale, but it made our voices almost unintelligible. We used the first effective helium unscramblers, electronic devices that synthesise speech, to be understood.
‘The temperature in the chamber also had to be maintained at 30 degrees because helium is such a good conductor of heat, you lost a lot of body heat in that environment.
‘We only had one or two degrees of freedom either way, otherwise you would be too hot or start shivering.’
The chamber was decompressed after 10 hours at 1,500ft, but at 1,150ft Peter suffered an inner ear bend, where air bubbles formed in his balance organs.
In an attempt to squash them and prevent Peter sustaining permanent damage they were re-compressed back to 1,500ft and beyond.
They reached 1,535ft and broke their own record in the process.
Peter recovered, and the pair spent 10 days decompressing to a normal pressure.
John says: ‘It was not too hectic so we had time to chat. I was fully aware of the importance of the dive and I asked him what he was going to do afterwards.
‘He said “I’m going to grow strawberries”.
‘I knew there was going to be a lot of publicity, and to me it was the achievement of a lifelong ambition.’
John and Peter remained friends, and years after their experience they met again in the early eighties, a mere 480ft below sea level.
‘We were at the bottom of the North Sea.
‘I was working as an offshore representative for Shell surveying a pipeline and he was the pilot driving the submersible.
‘It was a complete coincidence.’
At the age of 70, John shows no signs of slowing down. As well as chairing the Historical Diving Society, a national group, John is also an expert witness for diving accidents, an author and an academic – and these pursuits revolve around his first passion.
John says: ‘When I started to walk I started to dive. It is the first thing I was ever interested in.
‘It began in my early teens when I saw Hans and Lotte Hass on TV. They were pioneers in scientific marine biology and took underwater photography around the world, including footage of sharks, manta rays and coral reefs.
John got the chance to meet his idols when they were guests of honour at an annual conference of the diving society held at the Queen’s Hotel, Southsea.
‘I said something nice about Lotte in the speech I gave and she kissed me. She was about 70 at the time,’ he adds.
At 19 John joined the Portsmouth College of Technology, now the university, to study physiology and zoology.
After founding the sub aqua society there, John discovered the Southsea Sub Aqua Club and helped invent Octopush, a form of underwater hockey.
‘It is now played all over the world, it is the best game in my opinion.
‘Southsea was the best team in Britain and I was captain for a long time, during which we were unbeaten.
‘It is another of my life ambitions to see Octopush become an Olympic sport – there’s a high level of skill involved.’