In my case it's 50 years+ since I saw the book but I'm pretty sure the picture you saw was the Spitfire with the DB engine.
As the Merlin is upright and the DB is inverted, the reduction gear means the spinner has to be lower on the DB, not the other way round.
See the Buchon for an instant example.
Edit: Google EN830. I'm sure the picture that comes up in at least the first few links is the one in the book.
I wouldn't have remembered the title but I'm pretty sure you're right about the author. We had several of his books in my school library too.
Last edited by DHfan; 25th Jun 2017 at 21:19.