Perhaps coincidentally before Carden's prewar trip to France, one of the sales department's Army contacts might have mentioned that the Army was having a new type of AT rifle grenade developed, assigned the identifier "Number 68", and how would weapons like that be resisted by Vickers' tanks if the Germans were to develop one too?
The salesperson, being eager to have an answer for his Army contact since it would provide an excuse to pitch him again on available products, would pass the question on to Carden.
Carden, not being familiar with the #68 and how it was a "new type", would have asked someone from the Vickers gun design group who was considered to have a good grasp of armor penetration and explosive effects. That person likely would have struggled through an explanation of shaped charge physics, but been unable to satisfactorily answer Carden's questions about how their tanks might fare. So, Carden would have asked that someone from the ordnance group working on #68 be brought in to provide a seminar for his engineers, and himself. And, in that seminar, someone might have mentioned that the original developer of the shaped charge effect, a Swissman named Mohaupt, was working in France at Edgar Brandt & Company...a manufacturer with whom Carden was not familiar. So Carden might have added Brandt to his itinerary for the France trip.
Edgar Brandt might have personally greeted Carden, and they might have hit it off well...both being particularly focused on technical performance of their products, and not especially the best people at sales efforts. Brandt, with Mohaupt's assistance, might have better explained the shaped charge effect to Carden, and shown him some of the penetration-test plates they had sitting around the office. Brandt could have told Carden that the Germans definitely were working on shaped charge effects, though they were well behind France and England. And, Brandt could have shown Carden their design drawings for a family of 50mm, 60mm and 80mm gun-projected grenades, to be fired using special cartridges from the infantry rifle, the infantry medium machine gun and the 13.2mm heavy machine gun respectively, that they hoped would be ordered soon by the French Army.
Brandt might have mentioned to Carden that Brandt had heard that the #68 was going to have a flat face, and Brandt and Mohaupt would have explained that the shaped charge effect was much more effective if the device detonated at least
(as then understood) one and a half device-diameters away from the target surface to allow enough distance for the penetrating jet to form, and shown him how the Brandt rifle grenades would have a pointed front-cap to provide that jet-establishment distance.
And after the discussion with Henry Mohaupt was completed, and Carden thought he was ready to leave, Brandt might have mentioned that while it likely wasn't of much interest to the British since they primarily used high velocity two pounder / 40mm AT guns, the Brandt company also had a lot of activity related to a new type of subcaliber ballistic penetrator called a "discarding sabot" round, and they had received a contract from the French Army for 37mm shells to obtain better AT performance from French tanks with low velocity guns of that caliber. But, Brandt was especially hopeful of a contract for what they considered to be their best design yet, a 57mm tungsten carbide penetrator in a 75mm shell, able when fired from the ubiquitous Mle 1897 medium-low velocity 75mm artillery piece to achieve penetration results better than any other existing French gun.
At which point Carden knew that this visit was of great importance, because this might be the way for a low velocity cannon such as the 3 inch howitzer in the Valiant to be a universal gun, with both a highly effective HE round and a high-performance AT capability.