Not too sure about this one, but the factory did make several driveable scale models for 'favoured' VIP's children.
Not too long ago one of the magzines featured a Series 2 that had been made for a foreign Prince.
Or the famous Aston Martin that Prince Charles had as a boy?
Rebel Replicas produce a Range Rover, but that's battery powered.
The caravans were generally built in the late 60's'/early 70's as publicity gimmick for the showrooms - a dealer on the southern edge of Huddersfield still has one.
Harrods (as well as Hamleys; London) used to have them.
I'll ask on T&T if you're interested.