I admit I didnt watch the entierty. But i have a lot of respect for England and her institutions.
Still the point remains. That the police dont arrest someone is not because they do not have the authority to do so. They do. They can arrest IF they want to. And IF they arrest you, you cannot resist, regardless of whether you are in the right.
The citizen can hold the police accountable, but not until the Courts deem that citizen to have been unlawfully arrested. If you claim that a police officer assaulted you, that is something that must be proven in a court. Police may lose his job, but only AFTER the fact, and only after the Court has deemed you innocent. You cannot determine yourself to be innocent and thus refuse arrest. Thats not how it works.
No politician can step in to save you. Only the Courts and evidence.