[tcolvin]

Interesting, Steve, but could you explain, please, why the RAF wanted more Allison Mustangs/Allison engines rather than Merlin Mustangs.
Did the Allison Mustang have an advantage?

I understood the RAF insisted their aircraft performed at altitude, and this was the reason they rejected the P-39 Aircobra. (I have heard an opinion that the VVS had no such requirement, and therefore accepted the P-39, because most aerial actions in Russia took place below 15,000-ft).

Packard undertook in September 1940 to build Merlins for both the US and British governments. The first Packard-built Merlin was fired up in Detroit on a test-bed on August 2, 1941.

So the XP-40F must therefore have been fitted with a RR-built Merlin in June 1941.

And the MAP could have specified Merlin Mustangs from the get-go had the RAF wanted them. Which comes back to the first question above, as to why the Allison Mustang was preferred.

Tony