1. If you need to do an overtake, dominate the road space. They can't squeeze if there is no room to get alongside. From the vidoe, the skills in this area were poor.
2. Lights, it was a poorly lit area, and the "offended" rider had poor lighting, took no rear observation before moving out.
3. The whole confrontation was unnecessary, and simply provoked the driver into a worse mood, which is reflected in the cutting in incident (not excusing this), which brought danger to someone else!.
4. Lesson, take a note from advanced moto riding system, use a "lifesaver" glance before that final move, and when the traffic is as tight as this be aware what's going on around you. It's not all one way agression, as sadly we sometimes see in London (and elsewhere), but the people who get hurt are on tow wheels, where it's just body damage to a car/bus/truck.