myth I think
I believe this to be myth. The Griffin preceded the Merlin in lineage going way back. I'll say that again... the Griff came first as a twinkle in the eye and the Merlin followed by which time the sense of rotation had been sorted. Later there was a requirement for more power and more cubic inches. So in the time honoured way old plans were dug out. In the tradition of second-best tomorrow as opposed to first-best next year the Griffin was re-born. After all there was a war on.
The eminent author and historian who wrote under the name "John Winton" describes how the early jet years forced the FAA to retain piston-power to get off the aircraft carrier. The short-comings of the Griffon 45 and 46 were many. But ship-borne aircraft and their engines had their place in the scheme of things and the answer meant that something had to give...let's face it, what do Admirals and submariners know any way... of course they got the prop rotation wrong. I told 'em but would the listen? Etc etc. The reality was wartime priority.
In essence we believe the Admiralty diktat story because it is funny and people believe the Griffin must have been a second stage of development from the Merlin. Not so.
Where is Brian Abraham? Mine's a horse's neck snid
[See also R-R Heritage site]