The mystery of the sleeping centaurus

By Alison Mayor

It is one of the South Coast's strangest dives - a set of armed tanks and bulldozers sitting peacefully at 20m, but how did they get there? Alison Mayor tells how Southsea Sub-Aqua Club finally pieced together the full story of the enigmatic wreckage

The bulldozer would have made easy work of clearing the Normandy
beaches

The dive team receives a briefing

Resting place: Second World War Royal Marines prepare their tanks

Armoured protection: the mighty Centaur tank now provides a sanctuary
for marine life such as this large edible crab

Concrete busters: a 95mm high explosive shell, intended to announce
the arrival of the Allies with a bang

The tanks' final resting place in Bracklesham Bay

Pure power: the massive blade of the armoured bulldozer points up

Measuring up: Southsea Divers took many measurements which helped
to confirm the tank's identity

Friend or foe: a curious conger eel emerges from his Caterpillar
(bulldozer) home

As we descended down the line, the outline of a huge bulldozer appeared before us. Nearby, lying on its side, an enormous plough stood 3m proud of the sea bed. A few metres ahead, a curtain of shoaling fish parted to reveal two tanks, still recognisable and in remarkably good condition. Ammunition was scattered all around in the jumble of the debris field, a testament to the confusion that led to these wartime artefacts finding their way to the sea bed.

We were trying to establish exactly how the tanks and bulldozers came to be at the bottom of the Channel, eight miles south of Bracklesham, apparently without any sign of the vessel that had been carrying them. For years, it was assumed that they had slipped from a section of Mulberry Harbour, the closest Second World War wreckage to the tanks (Mulberry Harbours were a type of temporary harbour developed to offload cargo on the beaches during the Allied invasion of Normandy). We wanted to test this assumption and find out more about the machines.

With the blessing of the Ministry of Defence, membersof Southsea SAC began planning a full survey in earnest. Silent Planet kindly provided their dive boat Top Gun, and with the help of a grant from the BSAC Jubilee Trust, 25 divers were able to spend five days mapping the site in detail, looking for clues that may explain the mystery of how the tanks sank.

On our initial dive, we established that the tanks were not the commonly used Shermans we had expected to find. They were definitely British, but with a shorter-barrelled, large-calibre gun. Experts at the Bovington Tank Museum subsequently identified them as Centaur CS IV tanks - only 80 of these vehicles had been produced for use in combat. They were given to the Armed Support Group, a unit of the Royal Marines. Only two examples of these tanks are known to exist today - both stand as D-Day memorials in France.

The site itself is tricky to find, as the wreckage lies close together in a scour and only stand proud of the sea bed by a few metres, so the wreckage doesn't appear much above the general sea bed level on an echo sounder. The whole site is only 30m by 20m wide. However, once you find the site and begin your dive, you quickly appreciate the unique nature of the wrecks and how well preserved they are. Southsea members dive on shipwrecks all the time but these wrecks are very different, as the tanks and bulldozers are completely out of context without a shipwreck in the vicinity.

One tank lies upside down, while the other sits on its right side at a 45-degree angle. Thanks to their armoured construction, they are in excellent condition despite 64 years on the sea bed. Some track is missing on one tank, but they are otherwise intact. Both tanks have a distinctive 30cm round plate on their front sides - a unique feature that identifies them conclusively as Centaurs. At the back of the tanks there are tow bars for pulling the porpoises - waterproof sleds designed to be dragged behind the tanks to carry the extra ammunition they needed for their missions.

The two armoured bulldozers lie on their sides about 4m behind the tanks. They were intended for use on the landing beaches, to smash though German obstructions and push aside crippled tanks. One is completely intact, its five-ton plough standing 3m high. The plough of the other has broken off the second bulldozer, but lies nearby. These powerful machines had a winch on the back and huge hydraulic rams, which could have easily shifted practically any obstacle in its path. The driver's cab and the whole of the body of the bulldozer were covered in thick armour to protect against enemy fire.

The discovery of some sort of field gun had us perplexed for some time. A length of wreckage similar to a gun barrel was found near one of the bulldozers, but there was no evidence of a gun carriage. The team now believe this is the barrel of the 20mm anti-aircraft gun from a landing craft.

Each time we dived on the site, we discovered new artefacts: anchors, propellers, ammunition and other items all providing key elements of the puzzle. Once you start to delve into the story behind the sinking, you get a sense of the traumatic events that must have taken place. It's a dive that has all the vital ingredients for most Brits: unique war machines, a sense of mystery and the bonus of marine life. On so many wreck dives it's just a question of getting down there and then heading to the bow or the stern, but this is more complex.

Armed with the information from our survey and the advice of various experts, we began researching the Royal Marines' history, using naval war diaries and other historic papers related to Operations Overlord and Neptune. These files are now available to the public from the National Archive and can be viewed on request.

We quickly established that the Mulberry Harbour's floating pier could not have supported more than 100 tons of equipment. When installed in its final position each section was only designed to support a maximum weight of 56 tons, but the wreckage we had found would have weighed far more. So if they didn't fall from a Mulberry Harbour, how did they get there?

An entry in the 2nd RM Armoured Support Group War Diaries related that the regiment had boarded their landing craft tanks at Gosport, on 2 June 1944, proudly adding… 'an event partly witnessed by the Prime Minister and other visitors'. These Royal Marines and their flotilla of landing craft were to be part of J-Force, the predominantly Canadian assault force that took part in the landing at Juno Beach. The troops spent several days at sea waiting for the final orders to commence Operation Overlord. The poor weather led to a 24-hour postponement from the original plan, but the order was finally given and the ships set sail on the evening of 5 June 1944.

Reading through these fascinating documents, we found an entry reporting that on the night of 5 June 1944, one of the landing craft tanks had failed to make it across the Channel due to engine trouble, and had subsequently capsized while under tow. All crew and other personnel were saved and the craft was later sunk by RN gunfire to prevent it becoming a hazard to shipping. The J-Force records confirmed the landing craft in question had been carrying two Centaurs, two armoured D7 bulldozers, an armoured car and ammunition. There would have been 12 landing craft crew and another 39 Royal Marines and Canadian Army soldiers on board the landing craft.

There were 26 landing craft just like this one - each of them fortified with 50 tons of armour around the bridge, and with ramps fitted to their decks so that the Centaurs could fire their guns over the bow. The additional armour and positioning of the tanks severely affected the stability of the craft and heavy seas resulted in a number of overloaded landing craft being swamped.

In this case, we could surmise that the landing craft would have capsized quickly; the chains securing the tanks would have provided little resistance in preventing the 28-ton tanks from plummeting to the bottom of the Channel. The 50 or so people on board would have been pitched into the sea, though from what we now know, none of them died. For their many comrades heading to the beaches of Normandy, the day would tell a very different story.

Diving on Second World War armoured vehicles does seem a little odd at first - especially without an actual shipwreck nearby - but you soon begin to appreciate the sheer presence of the tanks and 'dozers. They are awesome machines, resting on the sea bed and surrounded by shoals of fish. This site is a true time capsule, and it has allowed us to piece together a forgotten episode in history. If you are looking for something different, whatever your diving grade, this site will have something for you. Southsea members have enjoyed the experience of the project and are pleased to have been able to finally tell the true story of the sleeping Centaurs.

Need to know
- Position: 50° 38' 32”N, 00° 51' 37”W. Eight miles due south of Bracklesham.
- Further reading: Dive Sussex - A Diver Guide No 40
- Depth: 20m
- Tides: slack-water site 90 minutes before high-water Portsmouth and 45 minutes before low-water Portsmouth.
- Local skipper: SC Charters:
http://www.southerncoastcharters.com
email: simonbradburn@hotmail.com;
tel: 07932 162721
- Getting there: from the A27 at Chichester, take the A286 and B2198 to Bracklesham Bay. There is a car park and slipway for launching from the beach (4x4 essential).