The book I read to research this post was Spitfire – Portrait of a Legend by Leo McKinstry and it’s a very good book. I got it from the library.
The spitfire almost never happened because when the first protype flew despite their expectations it wasn’t much faster than a hurricane. They went back to the drawing board and made some improvements and made it a lot faster. Hurricanes of course were a lot cheaper to produce. The german despite often being capable of going faster couldn’t go faster than 180mph because if they went faster than that they wouldn’t have enough fuel to get back. So the hurricanes and spitfires made short work of them. The germans didn’t control any decent oilfields so fuel was very much rationed. The british by comparison got fuel from the USA so it wasn’t rationed to the same extent. Also the germans hadn’t any proper bombers.