Bus driver did something similar to me once. Then he stopped at the next bus stop.Whether the rule is 1.5M or 6" doesn't really matter. I'm sure that any regular cyclist that rides on the road has had many incidents where motorists have deliberately run too close for no reason other than to intimidate the cyclist. I guess that's what the police are trying to eliminate. It's pretty obvious when it happens. There should be no excuses and instant prosecution for dangerous driving.
I've even had a bus do it, presumably because I held him back a bit after using one of those cyclists zones at the traffic lights. He half overtook me then pulled his front in as close as he could get to the curb so I had no option but to brake and let him go. There was no other traffic other than what was behind him.
They don't half scream and yell when you pull 'em across that little counter by the throat.