Shouldn't have been undertaking!! Although Fiesta should have checked mirrors better. There was no reason you couldn't have legally overtook from what I could see, rather than illegally undertaking in such bad conditions.
Driving a HGV well in excess of the 40MPH limit in place on the A75, overtook around a blind bend because they weren't able to put themselves into the gap that was far too small at both ends. No plate on the trailer.
May have been an M5. Therefore he's got special exemption for having such a monster of a car!