If you're not a professional spy photographer, the chances of randomly meeting up with a prototype on the road are rare to zilch – depending on your location, even more so if you're travelling at night when it's far more difficult to spot lightly camouflaged models.
Yet these two gentleman in a 2013 Audi S6 (that's the one with the 414hp / 420PS 4.0-liter TFSI V8), were able to tell apart a 2014 Porsche Panamera test car – likely from the LED lights at the back and the tweaked nose up front.
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