Wearing XF bodywork but measuring much shorter than a production XF, the prototype also sports a lower ride height and different exhaust plumbing, confirming that this is anything but an XF underneath.
The platform has yet to be confirmed, but current speculation has the small Jaguar using either a cut-down version of the XF's steel floorpan, or a scaled-down version of the Range Rover Vogue's PLA aluminium architecture.
Engines will likely include a 2.0 litre turbo petrol and a 2.2 litre turbo diesel, along with the supercharged V6 options available elsewhere in the jaguar range.
Speaking with Britain's Autocar, Jaguar brand manager Adrian Hallmark said buyers can look forward to a sedan that "looks and drives like a Jaguar", features the highest technology ever offered in the segment, the most efficient engines and the most refined feel.
“[we will] build the most advanced, most efficient, most refined car in that segment. Not almost as good as, but better than the best in the world," Hallmark told the magazine.
As for what it would be called, the internet rumour-mill says "XS" is a potential moniker.
Fitting for a luxury car? Maybe, but the more understated and refined nature of the Jaguar brand makes us think such a badge would be deemed too uncouth for a production vehicle.
Jaguar is known to have registered XQ and Q-TYPE names, and one of those is likely to appear on Jaguar's new C-X17 SUV when it reaches production.
Whatever it's called, expect Jaguar's small sedan to hit the market toward the end of 2015.