I have finally managed to complete the job after a severe hiccup. Fitting the bar was easy with the excellent instructions specific to my car model. Having chosen a dedicated wiring kit it was disappointing that wires needed to be spliced at all, but that is down to BMW. More clarity with the fact that the correct yel/blk wire in the vehicle loom must be chosen from at least three others using a lamp prod tester,would have been helpful. I had the battery off for two days but when finally reconnected the car could not be started and various errors came up. My local service engineer could not fix it neither could BMW Recovery before towing the car back to main agent. They found a damaged connector by the dashboard which I must have knocked while removing the trim panel near passenger left foot. It was not clear how this was retained. Because the fault had also left all lights on and Recovery team wanted the battery left connected, it became deep discharged and not recoverable. Total repair cost £550. I still did not have a working tow bar though. I had chosen the wrong yel/blk wire apparently. But even BMW had chosen the wrong yel/blk wire! They had used an LED trailer board tester which did not reveal the error. A sorry saga indeed.