Sideburn reader Adam Woods sent a link to this gif. I didn't recognise the rider, but, using my Columbo-like detective skills, worked out who was the last Pro singles rider to ride the class running the champion's number 1 plate. I knew it was Pro singles, because it's a red number on a white background. It was Stephen Vanderkuur in 2013. He was the last to run a red number 1 because most champions move up a class to Expert/GNC2 as soon as they can.
A quick google of those two clues threw up the video below, clearly the source of the gif. The engine's gone, locking the back wheel. Scary.
You're welcome. G