British car?
Sorry frederick, I overlooked your reply (the answer is Yes)..
so this was a one-off?
Yes..
Austin Landcrab prototype XC9001 1958 by Pininfarina
..and Yes - that solves it!
Well done; I'm looking forward to the day when someone other than Majeko solves one of my puzzles...!
It has a clear resemblance to the PF Cadillac Starlights from around the same period: