I might have said that a little unclearly.
If, for example, there is intelligence on my system that Berty Bloggs is driving a green Polo, VRM A999 CAB and he is driving like a douche with drugs on him, then I can't arrest him for that but it does open up grounds to search under misuse of drugs act. Stopping him in a vehicle would therefore need to be done by the RTA. However, if he was stationary as in the video (which I still refuse to watch, annoying git!) then he can be detained under the misuse of drugs act and driving off will be a different offence (but not fail to stop).
However, if I was to deal with the driving like a douche...different kettle of fish
Other offences are different again, depending on the level of intelligence.
It is seemingly easier to just get on with it than explain it
If a member of the public had pointed out to the officers that the guy was doing handbrake turns etc then they have evidence (independent witness) and then the summons route (and subsequent power of arrest) is there. If there was no offence disclosed, then that route is not there and he can leave.
The fact that he was driving around with a mobile phone was an offence though, so should have been picked up on really.
It was in North Manchester btw, looking at the people that he has been "interacting with" and I bet they know exactly who it is