Be careful - the 7 way round connector is meant to control electric trailer brakes. Range Rovers do not have trailer brake controllers built in (an example of a vehicle with built in trailer brake control is a Chevy 2500 pickup with tow package)
So this connector, in a Range Rover, will light tail lights, brake lights, and turn signals but it won't stop the trailer.
Trailers that don't have electric brakes generally use the flat 5 pin connector
If you want to tow a trailer with electric brakes you can buy a remote trailer brake controller that relies on an accelerometer in the vehicle and a radio connection to a box on the trailer that cycles the brakes. Look up wireless trailer brake control on a site like E Trailer