The Rover 400 didn't come with one either...
The Rover 600 one is a different shape and when I tried was going to take a lot of work to fit for minimal effect, although I'm not a trimmer so might be different for someone else I guess. I suggest would be better to custom build something onto the boot lid if that's what you want.
As for "kidnap" victims... I would be more worried about the stupid design of the boot hinges that would smash their skulls when you slam the boot... I've often wondered about swapping the hinges for something more streamlined and hidden like most other saloon boots that would give more usable storage space... but never got further than the thinking stage.