197 - Stuck Throttle?

My brother has recently purchased my 197, today he said that he had an issue with the car, in that he was driving in 6th gear approx. 40mph.

He described that the car essentially accelerated on it's own accord. He proceeded to press the brake and clutch to come to a stop.

However the car was revving to it's rev limiter, and had to be turned off. I've owned the car previously for 6 years and never had such incident.

Anybody else had similar?