Fitting Brake Controller to a P38 Range Pover

I have purchased a brake controller (Prodigy) for my P38 RR and was about to install - an easy job - when I noted that the P38 uses all 7 electrical connections. Land Rover in their wisdom also provide sep power for left and right running lights. Obviously I shall need to modify the wiring slightly to accommodate - but which pin is usually(?) used for the purpose of electric trailer brakes on, say, a Jayco camper trailer?