Some brief replies:
1. Yes, he did touch me. He twisted my head sharply to "show" me that there was "no traffic".
2. I accept that perhaps I should not have argued with him in the middle of the road. However, I was scared and angry because he was coming up very close behind me, beeping his horn and shouting. The fact is that I was reacting to his aggressive driving and his breaches of the Highway Code, all of which was unacceptable and unprovoked.
3. what you cannot really tell on this video is that the traffic is choc-a-bloc almost the whole way down Finchley Road. Although at this particular part of the video the traffic seems free flowing, it most certainly isn't. It's stop start all the way. So I wasn't really holding up the traffic. As the continuation of the vide shows (which I haven't bothered posting), within about 100 yards of the incident, the traffic returns to bumper to bumper.
4. I did think about filtering and then riding in front of him but, tbh, I was far too shaken up and just wanted to get to work safely.