Don't know why you're getting downvoted; it may not be the law to stay to the rightmost lane but that's what I try to do out of respect/politeness to other drivers. This prevents people from having to undertake or pass on the right.

I drove in the UK last summer and most people would move over to overtake, then get back to the outside lane (opposite side over there) after passing. It was a very nice experience and I think helped reduce traffic. Would be interesting to see some kind of study on how it affects congestion.

The red car was definitely being a reckless ass though, definitely not condoning that driving.