Chris Niarchos in the P1 is an accomplished GT2 race driver with one win, six podiums and a podium spot at LeMans. He was driving better and much more aggressively than Robert using all of the track in the process. Both of McLaren's test drivers were there with a 675LT and as luck would have it there was a "customer" P1 with a top class racing "customer" there as well.
http://history.fiagt.com/driverbio.php?countkey=50
Robert Serwanski in the One:1 is a MX5 driver.