When we shared pictures and a video of a silver McLaren P1 tester wearing a pair of discreet stickers that read “XP2R Prototype Vehicle”, shot by our spy photographers on the ‘Ring the other night, we admitted that, besides the red calipers, there was nothing different about this car over the Geneva show model and that we didn’t know what it was.

McLaren solved the mystery on Friday by telling Autocar magazine that the P1 XP2R is not a special edition, new version or a racecar variant, but simply a tester of the standard P1 that will soon be available and which combines a 3.8-liter bi-turbocharged V8 with a KERS hybrid unit to produce a combined 903HP (916PS) and 900 Nm (664 lb-ft).

The McLaren spokesman went one step further explaining the code names of prototypes to the publication: XP stands for eXPerimental and denotes early testers; the VP tag indicates Validation for later prototypes and PP is for Pre-Production models. The number “2” on the specific prototype reveals that it is a second test car, while the “R” indicates that it is a Revised prototype. So there you have it.

That doesn’t make the appearance of the P1 XP2R any less interesting, so we’ve added two new videos of the car (courtesy of YouTube users TouriClips and fastsportscardriver for your enjoyment right past the virtual break.

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