Fair point, but given that the Nazi intelligence network in the UK had been completely penetrated and turned right at the start of the war it would have been quite possible to circulate the idea of super-powerful radar stations or a leak in the Luftwaffe command structure to explain knowledge of German intentions. It would have been a bit more risky, true, and the RAF would have taken losses in defending Coventry. But that was Churchills' way, I'm afraid. As long as all his toys were intact, he wasn't bothered about a few peasants being bombed out! His contempt for the working class was consistently evident, before, during and after the war.