Yes, Cadwell, Barn Corner! Well spotted. The almost new 997 GT3 RS came past about 15 seconds later doing about 140 on the short main straight (I was doing about 100 down there). He was the fastest thing on the circuit, closely followed by another GT3 driven by an instructor.
No idea, sorry. It had the LED sidelights, and I seem to remember it was only one to two years old. I was talking to the instructor later (big guy, moustache), and he said the guy was a pupil of his and a very good driver, and the car was faster than his standard GT3.