My recollection is that the Mk IV infantry tank (A22 Churchill) was in development at roughly the same time as the Mk III infantry tank (Valentine). Chamberlain writes that the Churchill was "intended for service on the Western Front which, in 1939, was expected to be similar to 1918 as far as tank operations were concerned". I'm not sure what that means...did they think they needed an especially long chassis for crossing trench lines? Not sure. First used at Dieppe in action at Dieppe in August 1942 where most were lost as they couldn't scale the seawall (presumably more of an Intel fail than a tank design fail). I think they eventually saw substantial success when upgunned by ordnance depots to 75mm guns salvaged from wrecked M4s. Of course, Hobart made great use of the Churchill in development of his "funnies" for Overlord.