Much like spaceflight, aerospace or nuclear engineering, you need to retain local talent for national defense purposes. Being 70% as good is still way better than being 100% dependent and heavily leveraged by your opponents.
Demis Hassabis and Google's Deep Mind are all British in terms of location/talent, but they certainly aren't from a coorporate perspective (Deep Mind work might happen in London, but it is owned by Google, as US company)
(I don't know a lot about nuclear/aerospace industries, I'm guessing there more location centered just in virtue of being based around physical things, but I could be wrong)