Charles, Same thing happened to me last night on the M1.
In a friend's old panel-van (cause his surfboard won't fit in a MINI!) coming back from the gold coast, doing a little over the speed limit in the 100 zone, and a merc CLS passes us - we oogle a bit, and then try to break subtly as we notice the cop on the motorbike on the road shoulder up ahead. Flashing lights go on and he pulls out..... lucky for us he shoots straight after the CLS