That Rover in the photograph, owned by the Queen, is actually the regular sedan version. There was also a Coupe, that had 4-doors, and a slightly lowered rear roofline. IMHO it was a real looker, and now is worth collecting. Never seen one in Canada, they were quite rare in UK. Made 1970/1971.
So, the Mercedes was really a copy of the Rover 3 1/2 litre Coupe.
Whilst we're on the topic...the Chrysler 300 is a pretty good copy of the Rover as well - this itme the regular sedan version.
Cheers,
JR