Thanks Richard
There is a listing of "Rated Horsepower" for the 1942 Ford Flathead of 32.5, but I never understood how this figure was calculated.
Using your formula, I was able to calculate the same result for this engine.
So I would suppose that it may have cost 32 pound/annum for road tax on a 239ci Ford flathead.
And that on top of fuel expenses.
It's a good thing that times were so good in the UK post-war.
Would be interesting to calculate the modern equivalent cost using the same formula at today's prices. I'd imagine that we'd all be horrified.
Pedr