I guess it was up to the RN then (?)

From " The last ditch" by David Lampe:

"So few military vehicles had been brought home from France that the few mobile defence units that could be raised in the summer of 1940 had to rely on hired civilian motor coaches for their mobility. Eight hours´ notice was needed just to get these units on the road- more time than the first wave of Hitler´s invasion armada would have taken to cross the English Channel and unload its troops. The defence units would then have crept across the country very slowly, impeded by the absence of signposts."

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