I've done something very similar at CC in my Corrado days.
A Grant Motorsport Golf was using the day as a unofficial test day for their race the following weekend, and he was simply ignoring the normal track day rules about overtaking on the left/right/by consent/etc, and was overtaking (or trying to) in the braking areas. It was only when I saw him out of my side window did I realise that he'd tried to do the same to me, but had not spotted my car was not particularly standard. I was fortunate enough to notice him with enough time to lift of a little so that he didn't come straight into my driver's door, and went much deeper into the corner than I usually would have
Of course, this meant there was less grip on this part of the corner, and I went ploughing off the track onto the grass. Luckily the grass was dry and I manage to keep it off the tyre wall (but there is a footpath about halfway along that came as a bit of a shock), and rejoined the track right behind him, and stuck to him for the next 10 laps or so until he peeled off for the pits :x
For the rest of the morning I simply chased him at every opportunity, and I think he spent more time looking in his mirrors than learning the car or track.
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At another CC event there was this guy with a Golf VR6 who was giving it loads about being a great driver but never been to CC before. I offered to show him the lines and the dangers, and for 4 or 5 laps we did a follow-the-leader procession, getting a bit faster on each lap.
After the 5th lap or so he starts flashing his lights, so I pull into the pits and he says he's getting bored and wants to step it up a gear. Fine with me, so off we go for another series of laps, but starting at about 8/10ths instead. 2 laps in and he's following me through Hammerdown at about 100mph and the next minute he's disappeared. I look around as I brake for and drive through the next corner and can't see him, so assume he's gone off into the wheat field in the middle of the circuit.
I get back to the pits just in time to see the recovery truck going out, and 5 minutes later this sick looking guy returns with what's left of his VR6.
He claimed he simply understeered off behind me through Hammerdown and then did a few pirouettes along the tyre wall. The only panel without damage was the roof
The car was a right off, and he had no track day insurance at all, and it was a company car - and this was at the time that the car's were only 3 years old, so would still have been worth £15k.
We tried to cheer him up a bit by giving him some 10/10th and 11/10ths laps and showing him how fast you really could go around CC.