Actually the theory did get aired in rather more authoritative places - including a documentary on the BBC in 2000, summarised in this article in The Times.

That doesn't prove it's true of course. But then nothing has been proved in this case one way or another, except that there were two murders, for whom no one had been convicted in a criminal trial, and to which no one has confessed either.

Everything else is gossip and spin and guesswork.