A couple of years ago, on a trip upto pick up my stepson, trundling down the A1, sitting in the 2nd lane in a queue of traffic overtaking a couple of cars. Anyway, looking in my mirror I notice the car behind me pull in, only to be replaced by an Audi A4, flashing his lights etc, gesturing to move out the way, which does tend to piss me off, I won't take the bait, but I will stick at the speed I'm doing and be a pain in the arse, take my time to move over etc. So, this Audi comes past, 2 asian blokes in it, passenger givin gestures etc, just laughed as he screamed off.
After a few miles, the traffic slows to a crawl, and after a few mins of stop start, I notice blue lights ahead, and as we pass them, the very same Audi sits in the 2nd lane, parked in the back of a van...

In the past, in my mis spent youth, I would have brake tested someone who sat on my bumper.... Tap the brake, just enough to flash the brake lights, if they didnt back off, I'd brake, just enough to scrub off some speed, but enough they'd need to react pretty sharpish.