One of the first things I did with my rover was to buy a nice adapter. Didn’t require anything else, but I do remember they were hard to find.
It’s an older European standard (they’ve moved up to one with even more pins I believe).
Ill see if I can find the emails, but it was a long time ago...
Much nicer than hacking the original apart.

 

I cut the OEM 4 wire lead (that went to the OEM round connector by the hitch) from the OEM LR trailer wiring box & slapped on the 4 wire replacement directly to it wire for wire (same exact colors). Zero issues & it works great on all 3 of my D2’s.