HIDDEN BENEATH POOLE BAY are the decaying remains of some very unusual World War Two wrecks.
Normally divers would expect to find a ship or an aeroplane, not a squadron of armoured tanks scattered all over the seabed. So the obvious question is this: how did the 17.5-ton Valentine tanks get there in the first place Were they just dumped as part of an artificial reef project, or is there a more intriguing story behind their presence
For some years I have been piecing together what actually happened to the Valentine tanks.
The story begins in WW2 when Hungarian-born Nicholas Straussler, a mechanical engineer from London, came up with what seemed a hare-brained scheme to use floating tanks as a secret weapon against the Germans.
Straussler based his concept on the Archimedes principle. He devised a watertight canvas screen that wrapped around the tank’s hull. When raised to a height of about 2.5m, the screen would provide enough displacement to keep the big metal lump afloat.
The framework was strengthened by a maze of metal struts and compressed air pillars. A single 62cm propeller was fitted to the rear of the tank, giving a top speed of 4.5 knots in calm conditions.
Once ashore, a quick-release mechanism collapsed the screen and another lever retracted the propeller, changing the inconspicuous canvas boat back into a fighting machine.
The grand plan was to surprise the German shore defences during the Normandy D-Day landings (as they wouldn’t be expecting an armoured assault) and win the war.
Whitehall rubber-stamped Nicholas Straussler’s experimental tanks as a “top secret” weapon, and sealed off all manufacturing plants from the public eye. Tank crews from the 4th/7th Royal Dragoon Guards were selected for special training.
But the scheme had its doubters. If the flimsy canvas screen was breached, the floating tanks would sink like stones, drowning everyone trapped inside.
Operation Smash 1 began at dawn on 4 April, 1943, with B and C Squadrons simulating an attack on Studland Beach.
The tank-carrying LCTs had been holding position for most of the night, riding the heavy swell on the western side of Poole Bay. Top brass issued orders for the exercise to go ahead, even though weather conditions looked marginal, and the six-cylinder diesel engines roared into life.
Fumes and sea spray choked the atmosphere. Waves broke against the massive bow ramps as they began lowering into the water. One by one, the Valentine tanks rolled forward and disappeared into a disturbed sea.
The tank squadrons ran into difficulty very soon after launching. Waves began breaking over the canvas screens, and the bilge pumps couldn’t cope with the continuous flow. As a safeguard, the commanders ordered everybody out of the tanks and used the outside auxiliary steering mechanism for navigation.
Eventually water burst over the screens, sending six tanks plummeting to the seabed.
Not everyone managed to swim free in time. Some men were trapped beneath the collapsed screens as the tanks disappeared beneath the waves.
Although everybody had been issued with Davis breathing apparatus, this had never been used at sea, or in such an emergency. In the chaos that followed, six men lost their lives.
So the DD (Duplex Drive) Valentine tanks would never see action on the Normandy beaches, but the ensuing months saw a strange twist of fate.
Soon after the disaster, the regiment was re-equipped with US-built Sherman DD amphibious tanks, far superior to the outdated Valentines. They would give the Allies a much better fighting chance against the infamous German Tiger and Panther tanks.
Smash 1 had shown that, in certain sea conditions, floating tanks were vulnerable. If what happened on the exercise should happen on D-Day, the consequences would be catastrophic.
After the war, however, Major-General Sir Percy Hobart, Commander of the 79th Armoured Division, wrote to Nicholas Straussler praising the
DD tanks’ involvement during the Normandy offensive: “In my opinion they have been a great success,” he said.
Unfortunately rough weather conditions had prevented the tanks from being used on most of the beaches during the D-Day landings, but according to Hobart: “On two of the British beaches, they led the attack in conjunction with LCTs. This new technique of attack was remarkably successful. It came as a total surprise to the enemy, whose defences were overwhelmed with firepower.”
The swimming tanks also saw action on the North Bank of the Scheldt estuary and during the River Rhine and Elbe crossings. “They have been of great value,” Hobart concluded. “It is the most practical method, so far produced, of enabling standard fighting tanks to cross water.”
Over the past 10 years I have managed to explore all of the Valentine tanks in Poole Bay, including the elusive Boscombe tank. The sites are classed as beginner’s or shallow second dives. Most are no deeper than 15m, and they are usually teeming with marine life.
Conger eels peer from the caterpillar tracks, and hundreds on hundreds of prawns scour the 60mm armour-plating. Shoals of stripy pout circle the site, and there are even occasional visits from cuttlefish, sea bass and John Dory.
I could never understand why the turrets had been blown off, unless they had been deemed a hazard to local shipping, but I managed to track down BSAC National Instructor John Sturch, who knew the ugly truth.
Around 20 years ago, John was chief instructor for Poole Dive Centre, a BSAC Premier school. With so many divers filling their cylinders there, this was the central point for breaking news.
“I heard divers saying that live munitions had been taken off the Valentine tanks, and that they were lined up on the quayside in full view of the general public,” John told me.
These trophies were live 75mm shells taken from inside the gun turrets. Local police were informed, and the Navy visited John and asked him for the co-ordinates/transits of all the tanks. “They told me that they just wanted to make the tanks safe for divers,” he said.
John regularly used the Valentine tanks for diver training. “The tanks over by Hook Sands weren’t affected by tides, so we could dive on them at any time.
At only 10m to the seabed, they were just perfect’.
John was in Poole Bay with a group of divers when the Navy started “clearing” the tanks. “We were the first divers to visit the site after they had left. I cried when I saw what they had done.”
As John shone his torch through the stirred-up silt he could see hundreds
of pouting and the resident conger eels lying dead on the seabed.
The explosion had ripped off the gun turret, leaving a decapitated, mangled shell. The Navy proceeded to blow the turrets off four more Valentines.

JOHN KNEW THE POSITION of one more tank, but didn’t tell the Navy.
Six months after the devastation, he went to find his “secret” Valentine. The small 6 x 3m steel target showed on the echo-sounder but in a slightly different position to what he had remembered.
It then dawned on him that he had in fact found a second tank lying within 100m of the one he was after.
Over the years this second tank had also lost its turret, though this time to a trawler’s boom rather than a controlled explosion.
John was lucky. He found the bronze plate fitted to the tank’s mudguard.
“It’s similar to finding the ship’s bell on a virgin shipwreck,” he told me.
After seeing plates taken from the other tanks, he realised that his came from a different version.
“I think mine came off a Mk IX tank, because it’s embossed,” he said. “The others I’ve seen have been hand-stamped, and come off the Mk XIs.”
As wartime productivity was increased, there was less time to spend on details such as engraving.
I hopped aboard Sidewinder, owned by Bryan Jones of Swanage Boat Charters. Bryan offers a good variety of local wrecks and reefs, including John’s secret Valentine Tank which, with the turret still attached, is by far the best example.
The propeller, BESA 7.92mm machine-gun and brass fittings were plundered years ago, but the tank sits upright and is still pretty much in one piece. The turret hatches have been jemmied off, so it’s possible to peer inside and see how small and cramped conditions must have been, especially for a crew of four – driver, gunner, wireless operator and commander.
At the front on the starboard side (the barrel always pointed rearwards while travelling at sea) is an underwater guide rope that connects to the second tank.
This is a good 2/3-minute fin along a shingle seabed. This tank also sits upright, its upturned turret half-buried in the silt a few metres away.

JOHN RECKONS THERE ARE 11 Valentine tanks scattered around Poole Bay, but I have only ever found references to seven: the six lost during Operation Smash 1 and one other sunk somewhere near Boscombe Pier, in what I assumed was a follow-up exercise.
Once again I buried my head in the history books, and found that in the Studland Bay attack a seventh Valentine tank had indeed been lost, abandoned by its crew when it ran onto a sandbank.
It refloated (minus crew) on the next high tide and had to be sunk by gunfire to prevent it drifting ashore. This had to be the Boscombe tank.
I heard rumours that this lost tank was virtually intact and had rarely, if ever, been visited by divers. If true, this would make an exciting find.
Wreck-site co-ordinates are well-guarded secrets. Luckily I knew a fisherman who had heard from a colleague about a possible location. Chris Mowlem had been catching crabs and lobsters in the Poole Bay area for more than 20 years, and I had faith in his ability to find a 17.5-ton tank, but would the co-ordinates be accurate
Another boat had already anchored close by, and divers were getting into the water. After all this time, had I been pipped at the post
We circled the area, looking for the all-important echo “ping”. Then Chris said: “They’re searching in the wrong place.” We kitted up and jumped into the water as quickly as possible.
In my haste, I forgot to check whether Chris had completely closed my drysuit zip. I started to feel cold water seeping down my back – but it would take more than a trickle of water to stop this dive!
The seabed was covered in a fine layer of silt. I followed Chris’s fin-plumes over to the tank site. All I could see was a mass of broken, twisted metal, not the intact tank for which I had hoped.
We found the upturned turret a few metres from the main superstructure.
A tompot blenny popped its head out of the barrel to see what all the fuss was about.

MY VALENTINE TANK QUEST then led me to the village of Upton, on the outskirts of Poole.
I had been trying to trace a local diver called Steve Frost, but had been told that he had died in a motor accident some years ago. Then a casual conversation with a friend revealed that Steve was alive and kicking – and living just down the road from me.
Steve, an old-school BSAC diver, had been among the first to dive the tanks back in the early 1970s. “Most divers would use them as a quick 10-minute dive at the end of a deeper dive,” he told me. “They would just scout around the outside picking off any lobsters. Nobody was interested in going inside.”
Steve had visited Bovington Tank Museum to do some background research. It didn’t have an exact replica of a Valentine but it did have a similar version. “I saw the brass mudguard plaques, and was sure they would still be there, half-buried in the silt.”
He had snorkelled down, wrapped the shotline around the barrel and then checked out the mudguards. Sure enough, the brass plate was still there.
“It was a Mk XI DD Valentine tank built in 1943,” he said. “The plate had been hand-stamped.” This was one of two Valentines that had sunk close to the Fairway marker buoy. Steve and his buddy had then come up with another brass plate on the second tank.
“We managed to get hold of some ‘top-secret’ plans of the inside layouts,” he told me. The hatches were still locked in place but “we had a lumphammer and chisel, so off they came.”
He had taken off his BC and dropped it through an open hatchway. “My regulator hose wasn’t quite long enough, and I had to let go of the mouthpiece.”
Steve had managed to wriggle through and pop the reg back into his mouth. “It was so dark that I couldn’t see a thing,” he said. “I just put my hands out and grabbed anything I could.”

WHAT HE FOUND WAS a flare pistol, brass labels, compass, spare gun-sight prisms, headphones and even toothpaste and razors. “I was really surprised.
I thought the tanks had been on exercises and had bugger-all in them.” He had also discovered some BESA ammo and a stash of 75mm shells.
A few days later, when he returned to the tank, the shells had gone. Steve had no idea that they had been brought up by other divers and left “fizzing” on Poole Quay for passing tourists to see.
He told me that he hadn’t dived on the tanks since they were blown up.
“In some way I feel responsible for what happened,” he said.
I had found the very man who may well have instigated the whole chain of events. Steve no longer has any of the tank relics. Over the years he says he gave them away to friends.
This year I was shocked to find that the gun-barrel of John’s secret tank had broken off and was lying on the seabed. The marker-buoy line had been wrapped around the barrel for many years, so perhaps a passing trawler had snagged the line and ripped it off – or was it just down to wear and tear
In hindsight, I should have made more of an effort to remove the line and attach it elsewhere. It’s a shame, as this was one of the most significant features left on the tank.
For nearly 70 years it had been raised in salute to the six men who died during Operation Smash 1, not forgetting the thousands who lost their lives in the D-Day landings.
As a mark of respect, the Valentine tanks of Poole Bay should have been made a protected wreck site. It really is an unfitting end to such a remarkable piece of history.
I’m just hoping that John’s theory is right, and that there are more tanks lying on the seabed waiting to be discovered. If I ever find them, I’ll let you know.

Co-ordinates of “intact” Valentine tank: 50 39.424N ; 01 53.328W. Swanage Boat Charters, www.kyarra.com