Explanation of POD and Timeline
There's been some comment on AllanCamerons TL about tanks, and what they can do, so I thought I should perhaps clear up any confusion about how my chosen POD goes and how it affects the tanks. While it's all in the story, some of it might not be so obvious.
The POD changes the result of the 1934 EAF exercise to be a success. As a result, they carry on testing and exercising as they develop a doctrine. This is what they didn't do OTL, and as a result didn't really know what to do with tanks in 1940, at least outside of a local, tactical level.
They are basically going in the same direction as the Germans, but with a lower emphasis on speed and a greater one on protection. What the exercises showed them was that the idea of outflanking was good, as was the idea of finding a weak spot and exploiting it. However the growing use of AT guns also showed that they might also have to crack the defence if the unsporting enemy hadn't left a usable weak spot.
These changes drive a different tank requirement. They were already unhappy with the light tank, the exercises confirmed it was useless except as a recon vehicle, and the Spanish Civil War just confirmed that. But they still need a fast tank to outflank and exploit (cruiser), it just needs to be a medium tank. This leads to the Vickers A10* - about 18 tons, 40mm glacis, decent gun and can do around 30mph on the road. It's fast enough to exploit a flank or hole, but reasonable tough so the odd AT gun won't stop them all. In order to actually crack a defence, they need an infantry tank (the Vickers A11). Thick armour (although it's a bit lighter than the OTL Matilda), a big LV close-support gun (it's intended to be used as part of an infantry attack), and reasonably fast (the higher speed than OTL is because they want to open that hole as fast as possible, and a really slow infantry tank just won't do that). They also intend to be driving the infantry around, again for speed (and again just as they did on the early exercises), so the A11 is intended to do over 20mph.
So the needs of the new doctrine have changed the tanks. Not a huge amount, but noticeably so. They have also dropped the idea of light tanks, instead spending their money on the more expensive Cruiser and Infantry tanks. Since they won't have a load of light tanks, the cavalry will still need something, and the obvious solution is the armoured car. So they will build these for the cavalry, they are cheaper than tanks.
The final new piece is the large infantry carrier. OTL, they used a massive number of light carriers to move weapons, supplies, and so on. Here they will be buying some larger ones instead. They cost more, but they dont need as many. The Armoured Brigade infantry need something big enough to hold a squad. Again, no reason they couldn't have built them OTL, just that with the old doctrine they were looking at a tank-led advance/breakthrough, with not much infantry. The exercises actually had a far more generous number of attached infantry, so they just haven't reduced it.
What this does mean is that the tactics and composition of the tank force is noticeably different by 1938 - and will be more so by 1940. They actually have a lot less tanks, although more capable ones, so the BEF's layout will certainly change.
The other change is in tank supply. By adopting the new doctrine early, the only firm that can supply tanks in 1935 is Vickers. So Vickers have designed two useful tanks, and are busy building them. With those orders, they have upgraded their tank plants (as they did OTL, but to build different tanks this time). The (very odd) decision in OTL to spread tank orders around firms with no experience will change. Partly because their established supplier, Vickers, point out its horribly inefficient, and a system like the RAF Shadow Factories makes far more sense, and also because Vickers moved early to welded tanks, and most of those other firms have no experience. They will end up building components, and some of the tanks designed by other companies (like the Matilda) which are more suited to their methods, but there will be some larger tank factories run by the experienced manufacturers. Nothing revolutionary, this is basically what the RAF did (and in a somewhat different way, the RN). It just needed someone to point out a tank is not a mess-tin, and you need a specialised firm to build them.
This leads to a rather different BEF than in Allan's TL. A lot less tanks, different tanks, and a quite different doctrine. The changes will apply from when the BEF arrives, ie well before May 1940. What effect this will have... well, I am being careful to avoid the excellent Blunted Sickle results, and I also don't want to treat over Allan's ongoing timeline, but I now have a plan that will be different from both and different from OTL. What it is, you'll have to wait and see.
But I still have to be careful not to give the British too much. It's an awfully easy trap to fall into, but at least up to the point the dakka starts its not too hard to control. After the action starts, the butterflies take a serious hold and it needs a lot more restraint on my part.