Soldato
I've seen a few times where police have moved over to slow someone down and/or given them a stare/wave to slow down but not pulled them. Also seen an idiot brake check an unmarked police car that pulled out along side me, then paced me for a bit well ahead of the other vehicle, to force someone to slow down that was probably doing around 120 - but I'm pretty sure was going to let them go on their way after that if they'd continued at a reasonable speed. Other driver probably thought they were just a busy body though.
My only close call with Traffic they did exactly this. I was driving over the M62 and using my then GF 1.3 escort so hardly nippy up hill at motorway speeds. There was a woman driving similar to me who was driving something even more underpowered, like a 1litre fiesta or something, who was trying to go faster than me in general but repeatedly losing far more speed than I was and in effect kept getting in my way.
So I thought I will just do 85 for a bit get far enough in front of her that this doesn't happen. I sped up to about 85 and about 10 seconds later a whew noise and blue flashies for a few seconds. I pulled over to middle lane, then slow and they followed me across from 3rd to second and pulled alongside, looked at me and then accelerated away. I assume they had been somewhere not far behind and had seen the her speeding up and slowing down thing but I had lucked out and become the bigger issue at that precise moment once I hit 85. I drove spot on 70 for the next 30 mins or so, so the annoying driver got away from me