Could Britain have successfully launched Operation Sealion on itself?

Found some cursed posts from the past while thinking about the whole Nazi-Soviet unholy axis scenario:

Well, Stuart Slade's The Big One had the really dumb Halifax-Butler Coup, maybe they can spice it up by having the coup work only on the navy and then someone Sealion happens.


While I was ready to cast off that down the memory hole of alt history, I discovered that the Royal Navy's last mutiny took place in 1931, within spitting distance of WWII, and the Royal New Zealand Navy even had one shortly after the war. Both because of pay cuts, and one involving Marxists and Soviet sympathizers.

Not to mention the Royal Indian Navy had a mutiny in 1946 as well, though for obviously different reasons

So suppose that Britain was at world war against a continental alliance, probably socialist, to appeal to potential underpaid sailors. Despite the difference in political and social conditions, suppose the OOB was the same for all sides involved. If Red Germany tried to pull off Operation Sealion, how much of the RN has to defect in order to make such an invasion successful?

As a coda, no one in the second thread above commented on what if you threw in all of the Axis + Soviet forces, but also the occupied nation's navies as well, from Vichy to the Low Countries to the Norwegians and Danes.