For the first time ever, I phoned the police about a driver. I was following him on a 60 mph road and he moved over to drive on the right hand side of the road. A car coming the other way had to swerve onto my side of the road to avoid a head on crash. Gave me a moment, seeing that. Had he not swerved that would have been a head on collision, and at that speed.
Then he was driving like a madman, all over the road, speeding up, slowing down.
Got home, called 101, waited to get through...and got a row. I should have called 999 at the time.