The Jaguar XF has only one 12-volt power plug. First, cars need more than one outlet given the amount of electronics we carry these days. Also, the plug in the Jag is in the center console, under the armrest. This is an excellent location as this is where the auxiliary audio input is located but it doesn't work for a radar detector, it is too far from the windshield. Some manufacturers that fit a plug in this location also add a second plug closer to the windshield. Take Porsche, they "hide" a 12-volt outlet below the glove box in the passenger foot well on their 911 and Boxster/Cayman, a perfect place to run the cord for the radar detector. Even my wife's Subaru Legacy Wagon has two plugs, one in front of the shifter and one under the armrest.
I remember that our long-term Porsche Cayenne only had one plug and that was in an even worse location than on the XF, on the back of the center console facing the rear passengers. So, yes, even Porsche makes mistakes in this area.
Come on engineers, help us out here or maybe we'll have to start sending the speeding tickets to you. Radar detectors aren't much good when they're gathering dust at home.