It looks like an error of judgement from the driver, thinking he had more time/space to overtake you. Although he did manage to complete the overtake, its similar to drivers who stretch to overtake right before a junction then slam the brakes on to turn off.
I dont think anyone else has mentioned it and it may not be practical in London with much more traffic, but when im overtaken i tend to brake a bit to increase the relative speed, to reduce the time running parallel, reduce the time the car is (sometimes recklessly) driving to oncoming traffic and reduce the chance of being left hooked, because its very common that in built up areas drivers dont have anywhere near the relative speed they think they have.
imho its not anti-cyclist, its just mis-judgement of speed and maybe a bit of a must overtake mentality. In the street near my house (30mph) theres very very aggressive speed bumps that cars bottom out on if they dont crawl them and heading towards them, people are forever trying to overtake me mis-judging it and end up hitting the bottom of their car really really hard on the speed bump because they dont want to back out of the overtake.