It is fascinating to me to see the way technology developed and then devolved from the 1920s through the ’50s. The P-type had an overhead cam, cross-flow head and supercharger, while the T was overhead valve head with intake and exhaust on the same side, and normally-aspirated. 

This despite tremendous technical advances in the WWII era, when dual overhead cam engines were made literally bullet-proof for use in fighter planes. 

And the trend was not unique to MG or Great Britain. Remember the Hudson Hornet was “ground-breaking” (and race-dominating) because of a simple chassis innovation–welding the floor in below the frame members instead of above to create the low and sleek “step-down” design. But the engine was a flat head, valve-in-block unit.

I believe the war’s end created two contrary imperatives, the first being the well-known corporate mission to quickly fill pent up consumer demand. Everyone talks about that, particularly the British car companies’ “export or die” policy.

But the second imperative was to build cheap and fast. Building cars to a price-point was the newest and most pressing engineering challenge, and it was particularly difficult after nearly two decades of cost-plus military design.

The engineers, I believe, could not readily wrap their minds around this challenge–the design of the thing itself being significantly subordinate to the design of the assembly line, the efficient designation of tasks and the limitations of tooling that had to remain “in spec” for many more cycles than what was used for military stuff. So instead of adapting the lessons of military hardware to cars, they grabbed for older, proven consumer technology and punted to the marketing team, which duly tarted-up the “innovation” claims with rhetoric that was frankly laughable. 

This phase lasted for three decades (in America and GB, at least), and did not begin to change here until the threat of Japanese cars (overhead cams! but cheeeep!) and mandated emissions controls forced the engineers to start actually thinking again. 

–not to say that car engineers had much agency throughout this period. . . .