2 September 1941. Inveraray, Scotland.
The A17 Tetrarch DD (Duplex Drive) sat just behind the ramp that was beginning to lower. Previously the A17DD had shown the capability of swimming over a large body of water, ‘lowering its skirts’ and then going into battle. The next phase of testing involved the tanks being launched at sea and swimming into the beach alongside landing craft.
The three Royal Armoured Corps' Squadrons of the Special Service Brigade (more commonly known as Commandoes) were keen on getting their hands on some of these ‘swimming tanks’. They were being equipped with the normal Tetrarch which would be landed on the beach by normal Landing Craft Tanks. The capability of swimming ashore in the first wave with the infantry was a whole other possibility.
The six man crew of LCM 4 and the crew of the Tetrarch had been talking a long time into the night the previous day about the procedures that they would use. There had been plenty of straightforward tests so far. The tank had driven into the water and ‘swam’ around before returning and exiting the loch. Then the tank had been loaded into the LCM and left the ramp, straight ashore as any tank should be capable of. The test after that was pulling back from the shore to a depth where the tank sank up to the bottom of the buoyancy skirts and then driving ashore. Today was the day when the tank would roll off the ramp and into water where it would have to float, before setting off for the shore.
The driver in the tank couldn’t see anything because of the floatation skirts. Therefore, he wouldn’t be the only man on board to go through this. The tank commander would have to sit on top of the turret to be able to see and give the driver directions through the tank’s internal communication system. Both had been chosen as they were strong swimmers. They had been issued with, and trained to use, emergency Davis submarine escape apparatus, which had been adapted by Siebe-Gorman Ltd. Their confidence in the equipment had been enhanced when a driver had accompanied them under the water using the breathing apparatus. They were also assured that a boat would be immediately on hand, with the diver ready to help if needed. They’d chosen a part of Loch Fyne where, if the tank did sink, it wouldn’t be too deep for recovery, of men or machine.
It was a calm day on the loch, just a fine drizzle (known locally as ‘Scotch Mist’) falling. The driver and tank commander were rehearsing the procedures once more and double checking the communications. As the LCM reached the planned point, the driver started up the engine.
The cox’un got the order from the Lieutenant commanding the Landing Craft to lower the ramp. The engines were already stopped and the anchor dropped. All round, fingers were crossed. The tank commander watched as the ramp lowered into the water. With a wave from the RNVR Lieutenant, the tank commander ordered, “Driver, forward…slowly”. The engine revved and the tank began to creep forward. Passing the point of no return the two men had the sickening feeling of the tank leaving a solid deck and relying only on Archimedes theory of displacement to stop them sinking to the bottom of the loch. With the order to ‘Halt’ the driver disengaged the tracks. The tank wallowed, floating on the calm loch. With no signs of catastrophic failure, and no sign of major ingress into the tank from below, the tank commander ordered the driver to start the propeller. The tank began to make its way slowly towards the side of the loch, when the tracks hit the bottom, the driver re-engaged the tracks and brought the tank ashore, accompanied by cheers from all those watching.
Among the spectators on the shore was Major James Simon, OC B Squadron SSB. He was laughing with relief and cheering with everyone else. A civilian moved up beside him and as the cheering died down, introduced himself as Sir John Carden, of Vickers. While Leslie Little had been the main designer of the A17, Carden, as chief designer was keen on knowing what the users of his tanks made of them. Simon, a long serving professional Royal Tank Regiment officer knew how important Vickers tanks were to the Regiment, or Corps as it still was in his mind. Simon knew that honesty above all was crucial, he and his men would quite likely face the enemy in these tanks.
Lighting up a cigarette gave him a moment to gather his thoughts. He began noting it was an improvement over the Vickers Light Tank Mark VI. It wasn’t any better protected, its speed was slightly better, which was just as well. The track system was bit complex, but at least it carried the 2-pdr gun, so was more like a tank than an armoured car on tracks. Carden asked if it was the tank he would want to swim ashore against a defended beach? Simon had to admit it wasn’t. From all that’d been coming out of North Africa about German tanks, the 2-pdr wasn’t going to be enough. He was of the opinion that the 3-inch howitzer on Close Support tanks would be a better choice for supporting infantry, they’d be more likely to need to attack bunkers rather than other tanks. Though, he commented, a proper dual-purpose gun that could fire both HE and AP rounds would be even better. Carden nodded, this was no new idea from the users of tanks.
Carden asked him if he’d had any experience on the Valiant I or I*. Simon did, and he knew that the Valiant II was likely to appear with a bigger gun soon. Carden nodded, this was indeed true. His question was, with the theory proved by the Light Tank, how about a Valiant DD tank? Simon snorted. The thought of making a much heavier tank float was a hard idea to get his head around. His answer was ‘of course’ any tank commander wanted the best tank he could get. The Valiant was currently the best, especially if the Mark II had an improved gun, so that is what Simon would want. The plan was that three squadrons of the Special Service Brigade would be equipped with a mixture of Valiant I and Tetrarch. If the Valiant could be adapted as a DD tank, then all the better. Carden nodded again. It confirmed something that he had already been thinking about. Major Simon then gave him something else to think about.
When the Tetrarchs were coming off the landing ramps of the LCMs, they were often having to cope with up to three or four feet of water, sometimes with waves, even higher. The fitters in the squadrons had been bodging together various ways of dealing with the water, trying to make sure that nothing important, like the air intake and exhaust, would be swamped. Carden had one of his assistants with him, and asked if the Major might be in a position to allow him and his assistant to see these solutions. The idea of the need for a tank to be capable of wading through deep water, even over rivers and streams, would be worth considering.
One of senior NCOs led the two civilians to the Tetrarch DD to show them what they’d had to do in addition to fitting the floatation skirts. All apertures had been sealed and vital equipment had been masked. Extensions to the exhaust and air-intakes had been extended with trunking made from lightweight steel. In the engine compartment the spark plugs, magneto and other electrical part had been protected with mastic and tape. All the engine hatches were likewise waterproofed. The first few times the tank had been tested in water, various leaks had been found and then sealed up. Carden’s assistant took notes of everything.
Carden remembered that an A9 had been tested in 1940 at the Experimental Bridging Establishment at Christchurch. To see if a tank could cross a river underwater, a 20-foot-high periscope-like attachment had been fitted to the engine compartment. This concentric tube had brought down fresh air to the engine compartment in the outer tube, while exhausted air was returned up the inner tube. On the outside of this tube was another pipe that carried away the exhaust. If memory served him right, Carden believed the test had been successful, but not taken any further. That meant that there was data around that would be helpful in making the Valiant II more easily adapted for deep wading, not something that anyone in the desert had thought about. If a Light Aid Detachment had on hand a stock of pre-prepared waterproofing accessories, and a pamphlet with the information, then preparing tanks for a river crossing would be made much easier.
One of the senior officers at the test came looking for Carden, their car was waiting to take them back to the hotel they were staying in. Carden shook Major Simon’s hand, thanked him, gave him his business card and asked if he had any other ideas, that he, on behalf of Vickers would be happy to hear them. The Major saluted the civilian along with his superior officer. Someone in the position to do something about improving tanks was listening, that was pretty much a perfect end to a perfect day.
