Some historians like to come up with nonsense like that so it can pass as "original thinking".
"Gee, look at me, im the 1st one to think of it"....
Seen it before.
#1 The Royal Navy could not effectively oppose an invasion without air cover.
#2 The RN could not oppose an airborne assault (paras and landing forces) on southern Britain, or their resupply.
The presence of the RN certainly cannot be dismissed, it would not have been an easy task for the Germans to resupply their follow on forces, but the authors overstate their case. I will say that without a RN Britain would have been doomed, and it did its part, as other branches of the military did as well.
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