I promise that this is my last post on this subject - i have found another web forum where this car is discussed, and there is the usual confusion and misinformation. The claim is that the first Saxon was a purpose-built FJ car with a BMC engine, and the second car was the converted F3 Mackson with the DKW engine. I find this hard to believe - why would you give up a modern race car for something which had been built in 1952?
But I have found a photo of this "other" Saxon, supposedly built by the same man. It could be a new puzzle for me, but the image is so small that it isn't really suitable. So here's the mystery BMC engined Saxon, apparently built by Scott-MacArthur before he converted the Mackson.