...the rumours actually caused such a stink in the summer of 1940 that Winston had to manke two statements in the House about it AND order an investigation...the results of which a party of officers spent the summer wandering back and forth along the South Coast of England following the rumours; the "event" always seemed to have happened at the NEXT town up...or back down...the coast, and the officer in charge of the clean-up had always left the area for somewhere else...As most of the esteemed members here that have reply point out, the value to Britain of knocking out any attempted landing was huge, and I have no doubt that the government of the day would have made full use of it.
What's notable therefore is that despite all the rumours, the government of the day couldn't make use of it!
Peter Fleming spends quite a few pages discussing the up-to-1957 history of the rumour...