On August 18, 1966, Philip Kaye was nearing the end of a remarkable physical feat which would forever etch his name in the record books.
The sales engineer from Huddersfield was close to completing a 16-hour-long swim across the English Channel - his third attempt.
Having set off from the French coast, determined to become the first man to swim the shipping lane using the breaststroke, he had already encountered all the usual challenges; jellyfish, sewage and the sheer physical effort.
But as he approached Kent’s shoreline and the completion of his achievement, he was, in his own words, "depth-charged".
Two miles away, a salvage team was carrying out a controlled explosion on a sunken munitions ship off the coast of Folkestone.
The power of the blast was so strong it nearly knocked the Channel swimmer unconscious.
"I got a pain in my head and the sensation of being beaten with dozens of sticks," he told reporters at the time. "I never saw the explosion, but the tremors were terrific. I had a pins-and-needles effect for several minutes."
The explosion had sent a 300ft column of water shooting into the air and shook buildings in nearby Folkestone.
Yet, as the 29-year-old swimmer completed his remarkable feat shortly afterwards, he should, perhaps, have considered himself lucky.
Because a year later, a similar controlled explosion would have probably killed him.
Such was the power of the blast almost exactly at noon on Saturday, July 22, 1967, it registered on the Richter Scale - the measurement tool to gauge the strength of earthquakes. A tidal wave was reported, windows smashed and ceilings collapsed across Folkestone and Hythe - some four miles away - and a 20ft deep crater was left in the sea bed.
It is a remarkable story and one which those who live anywhere near the infamous SS Richard Montgomery 'bomb ship' off the coast of Sheppey, should take heed. Especially given the cargo of the Montgomery is believed to be on a similar scale.
In fact, it is due to what happened 11 months after Mr Kaye’s successful swim, that any attempt to salvage the Montgomery's deadly cargo was replaced with a non-intervention policy that persists to this day.
So just how did such a blast bring "panic to Folkestone's town and chaos to the beaches", as newspapers reported at the time? And what does it tell us about the effect of any similar effort on Sheppey's most famous wreck?
The SS Edgar Wakeman had been built in the sun-drenched dockyards of Beaumont, Texas. The oil-burning steamer, designed for carrying cargo, was launched in 1943 and quickly found itself part of the war effort.
In 1944 the US government chartered the vessel to the Polish government-in-exile; forced to flee after the German invasion and occupation and which based itself first in France and then London. It renamed her the SS Kielce after the Polish city.
It sailed from the States, via New York, to Liverpool and was then called into duty shuttling cargo around the British coastline during the conflict.
When hostilities ceased, the US government used the vessel to transport ammunition and bombs from Southampton to the port of Bremerhaven on Germany's north coast. They were destined to supply the US troops stationed in the country.
However, as it travelled along the south coast, just off Folkestone, on the night of March 5, 1946, visibility was poor. And in the sleet and rain, the 250ft-long vessel collided with the British steamboat the Lombardy.
As the Kielce began to sink, her 32-strong crew were all able to escape - fearing an explosion - and board the Lombardy, itself badly damaged but still afloat.
Two tugboats sent from Dover to aid the steamer towed her - and the survivors - into Deal.
One of the survivors, who had feared the worse after taking a lifeboat and found himself drifting aimlessly in the Channel, was also picked up by the tug as the Kielce was lost beneath the waves.
It was said at the time to have a "full cargo of bombs and ammunition" although a full manifest of its cargo was never traced.
It would be years before the Kielce was spoken of again.
She was far from the only ship with potentially deadly cargo which had found a watery grave off the Kent coast.
The English Channel's strategic worth during the conflict left its seabed littered with the wreckage of war and it was only in the early 1950s contracts started to be handed out to salvage companies for the removal of a number of wrecks.
In fact, when her wreck was first identified it took some research to not only identify her but to ascertain she was likely carrying explosives.
It would take another 10 years before the Folkestone Salvage Company won a contract, in 1966, to raise the wreck - and make safe her deadly cargo. The same company, coincidentally, who had disturbed Philip Kaye’s swim.
Initial work went smoothly. Efforts to clear the collapsed hull plating all went to plan, with the salvage experts firing two cutting charges on the hull without serious effect. The third, however, would be both dramatic and devastating.
It was at 11.59am when the fateful third charge was triggered - with disastrous consequences.
The Kielce, just 90ft below the waves, was sat on a silt seabed - and it was through the Earth's very crust that the bulk of the enormous amount of energy was dispersed. In other words the explosive power went down and along rather than simply up, along with a 500ft column of water.
Captain Mike Fagg of the salvage company, recalled for the A Disaster Waiting To Happen film on the Montgomery wreck: “We had done operations like this before and were expecting a small ripple and some spray. Instead, we had a huge plume of water and phosphorous bombs raining down on us.”
So powerful was it, that the tremor it sent was picked up on seismic monitors an incredible 5,000 miles away - to give a sense of distance, that's equivalent to central China.
The Maritime and Coastguard Agency report in 2000 on the SS Richard Montgomery, discussed the Kielce blast. It said: "The seismic effects of the explosion had been recorded by at least 25 observatories, throughout Europe and America, out to a distance of nearly 5,000 miles from Folkestone, and from these records, using techniques which were developed for cataloguing the severity of earthquakes and other seismic disturbances, a magnitude of 4.5 was allocated to the explosion."
For the good folk of Folkestone, enjoying what had been, up to that point, a quiet summer's day, the scale of the blast sparked panic.
According to national newspaper reports at the time "hundreds of families telephoned the police saying a 3ft wave had just swamped the beach they were on, washing away clothes and cameras".
The blast rattled window frames, displacing the glass in many and bringing down ceilings in Folkestone and neighbouring Hythe. Chimneys crumbled and roof slates became dislodged.
The Maritime and Coastguard Agency report explained: "There were a few reports of a 'tidal wave' hitting the Folkestone beaches, resulting in a small number of successful claims for property damage on these beaches, although it has been computed that the amplitude of the resulting sea wave caused by the explosion would not have been greater than about 2ft".
Still, an unsettling sight if you were out for a paddle.
According to the size of the elliptical crater it left on the seabed - some 20ft deep, 153ft long and 67ft wide - it is estimated it was caused by explosives amounting to two kilotons - the equivalent of 2,000 tonnes of TNT.
Reports added that staff working in the Folkestone civic centre thought the explosion felt so powerful they assumed their boiler in the basement of the nine-storey building had exploded.
A local councillor at the time, JD Banfield, who ran a hotel on Folkestone's cliffs described the explosion as "like an earthquake" adding he "warned my wife to be ready to get out in case the building collapsed".
It was probably just as well no-one was planning to swim the Channel on that day.
Yet despite the damage, and a handful of people being treated for shock, remarkably no-one was injured.
The scale of the blast, however, would change the approach to clearing sunken bomb ships; namely, leave them alone.
And that, of course, is just what they have done with the Montgomery, lying on a sand bank in shallow water about a mile-and-a-half off the coast of Sheerness.
Professor David Alexander, professor of risk and disaster reduction at the University College London remains mystified at why nothing has been done by successive governments to make the Montgomery wreck safe.
He says estimates some years ago put the cost of clearing the wreck at £40 million - a figure now likely to be multiplied many times over with any attempt coming with a profound sense of danger.
He explained: "Controlled detonation of the cargo is out of the question.
"To build a sarcophagus, Chernobyl-style, over the wreck would probably cause structural collapse onto the bomb-racks. Similarly, to build an 1,800-metre-long coﬀerdam [a structure which would allow water surrounding the wreck to be pumped out] around the wreck would disturb the stability of the ship's superstructure.
"On the other hand, extracting the bombs and making them safe would take at least six months and would, following normal procedures, necessitate the evacuation during all of that time of about 40,000 people. It would be a hazardous occupation that would require diﬀerent techniques for diﬀerent kinds of bomb.
"In the case of the Richard Montgomery, the level of uncertainty virtually precludes any kind of rigorous assessment of risk, which would be a necessary ﬁrst step in determining the right course of action to govern it."
Many may ask would the damage to a few windows and chimneys more than 50 years ago – such as was the case with the Kielce - be a better option than fearing an unexpected explosion today?