There's some serious conjecture involved here - but this might be our first view of Jaguar testing its forthcoming hybrid platform technology, albeit in the somewhat unlikely guise of an XK.
The car was photographed testing at the Nurburgring, where our spy photographers reported that it was uncannily quiet - without the V8 soundtrack you'd expect to hear from a hard-working XK.
Of course, it might just be a particularly well-silenced mule for the forthcoming facelift of the XK - or even an early installation of the 2.7-litre twin-turbo diesel that Jaguar is believed to be preparing to offer with the car.
The car is listed on the DVLA database as having CO2 emissions of 0 g/km - but this is confirmation of nothing other than the fact it's a prototype, making it exempt from current emissions taxation.
The car's front and rear bumpers are both different from those of the current model.
Jaguar and Land Rover are working to develop hybrid drive systems for both brands, although it's likely that Jaguar's system will be a conventional 'mild hybrid' set-up using batteries, while Land Rover is still experimenting with the use of capacitors.