Mr Planemaker's Flying Machine (by Sheilagh Watkins)

(Amazon UK link) I had not heard of Sheilagh Watkins, though she's apparently quite a prolific writer. However her book ‘Mr Planemaker’s Flying Machine’ was available free for the Kindle in 2011, and the title intrigued me. So I downloaded it. It sat on my Kindle for twelve years, unread, until I picked the title at random from my lengthy list of unread books, and read it on a recent flight. 
I probably shouldn’t have bothered. Or at least, I should have checked the blurb. It’s not biographical or...