Theoretically, the more armoured the gun shield was the more vulnerable it should have been to 2 pounder AP shot, as the more likely it was to have caused the latter to shatter after impact. E.M.C. Clarke refused to put the 2 pounder APHE round back into production as he reckoned that its shatter effect was lower than that of the the AP round. There is an incorrect belief around that AP solid shot was supposed to penetrate a tank and then bounce around inside, but this was not the case. The purpose of AP shot was supposed to be that it shattered as it emerged from impact and then blasted the inside of the tank with shards, like a shotgun. When the Germans fitted face hardened armour this had the basic effect of pre-shattering the AP solid shot before it entered the tank. Regarding the 37mm HE round, it's also worth noting that the 5cm HE carried in the Panzer III held no fear for the British. The most readily available solution was to use the 3" Howitzer in the CS tanks against AT guns, but the British had hypnotised themselves into the belief that this was an occasion-specific smoke weapon, so we'll never know how effective it may or may not have been.