On the P-51 as an escort fighter: the story I know is that the British purchasing people wanted P-40s, because they were in production; it was suggested that North American had the spare manufacturing capacity, but when they were approached said they could do something better than the P-40, and did so. I know it wasn't specified or designed as a long-range escort fighter, and I understand that it took quite a bit of modification, including a somewhat marginal rear fuel tank, to make it one. My point was that rather that, since once critical factor was the Merlin supercharger, an escort fighter might have been designed in the UK, but wasn't because it wasn't in the doctrine; and the P-51 was developed into an escort fighter on an American initiative.