But in my case, I indicated and pulled out. Then, when the car reached me, he started to flash to suggest I was in his way.
you were in his way, he was a police officer following someone he wanted to pull over.
If I had known he was in an unmarked police car (ie if his blue lights were flashing) I wouldn’t have pulled out
There would have been a perfectly good reason he didn’t use his Blues. Like not alerting the driver of the vehicle he was following that they were being followed, until he was in a position to pull them over.
As it was, as far as I was concerned, he was just a knobber being a knob because my using the outside lane had gotten in his way.
But rather bizarrely, even after you realised the actual situation was different, you still don’t see a difference 😐
He flashed his rear blues, to let you know he was Police, this was to let you know he wasn’t just some idiot tailgating, and that he was trying to pass for a reason.
(How you don’t realise all this really is beyond me 😐 )