Lately I was revisiting some of the late-war British AFVs armed with the 17-pdr.
IIRC, British late-war tanks designs already had their foundations laid down on requirements made in the aftermath of Fall of France, so they were pretty much optimised for what was available at the time- 2 pdr and 6 pdr- for their main guns. 6-pdr worked well enough against the primary Axis tanks back then, and 17-pdr was pretty much prototypes pressed into combat at that point. Only when they made it back to the European mainland did that decision really come back to haunt them.
Did Germany possess any tank design that, if placed into production, would have motivated the British into putting a 17-pdr on a tank (or at least coming up with a 77mm HV) sooner?
Kind of similar line: the Russians knew all about the Tiger I well before it arrived in North Africa, but they didn't share their info when asked about a rumoured German heavy tank by allied intel. What if they had?
British Intel got wind of the Tiger I, to the extent of knowing it's weight, armour and gun calibre, in early Nov. 1942. They asked the Moscow mission to obtain more details, but the Russian didn't respond until after April 1943, by which time the British had already captured one in North Africa. The Russians had first engaged one in August 1942 outside Leningrad.....
It's not so much the sheer lead time (4-5 months) that's important as the timing: in between the Russians meeting one and the British meeting one, the combat debut of the Sherman happened, which led to an unfortunately complacent decision to standardise on the American 75mm for future British tanks. Given the inertia of the British requirement-design-development-production process, this was still having a serious effect long after it was shown to be flawed.