It’s a mystery to me anyway. It turned up when I was researching clay models.

The associated images show lots of Austin vehicles and other prototypes. I suspect it’s a rejected design for the Maxi or Allegro. Presumably Driven to Write’s readers know more. As ever, it looks like a fabulous missed chance from Austin-Rover’s immense catalogue of missed chances.
“Brian Borchester-Brom, head of Canadian marketing rejected Project Foal because he hated the rear door handles and also did not see eye-to-eye with Len Lennington, head of advanced mid-sized vehicle planning and insisted on a 4-cylinder saloon with doors from the 1300….”