hail brian and snid
To clarify... it is the lineage that counts. The first thinking went on before the Merlin.
While the focus was on the Merlin there came about the need for more power and more cubic inches. But the factories and the ministries saw to pressing needs and the inspiration for the Griffin came from earlier ideas and tooling. If the Griffin is anything it is a prequel rather than a sequel, strange though it may seem. That is what I meant by saying the Griffin pre-dates the Merlin rather than being a lineal descendent.
Without diverting too much effort away from Merlin production jigs and tooling could be refined into an engine that among other thing "turned the other way". But it is not progress to change gears, firing order etc for no good reason except in the middle of a war it makes sense to put to good use what you have to hand. You make do. Second-best tomorrow rather than first-best next year as Watson-Watt had it.
Bill Prentice [also spelled Practice and Prattis] left me all his work from the 1930s until 1948. R-R chose for some reason to destroy almost all of this ostensibly to clear out useless files. Alas a spirit of revisionism seems to have motivated R-R also, almost malice you might say. It is as if someone "got his own back" and consigned records to the dustbin rather than posterity. Certain it is that much has been written out of history and great work destroyed for the pleasure it gives lesser souls. But... wait for it.
Bill never threw anything away! If the vaults at Derby are empty mine are still full. All 18 years worth.