Police practice at marches / protests / riots

So this week I have been following the live blog of Guardian write Paul Lewis at the inquest regarding Paul Tomlinson who tragically died at the G20 protests in April 2009 after being struck by a policeman. I was also chatting to Nick over on my lomo account about police practice in general at such events and I have been thinking about this sort of thing a lot this week as a result. 
The Ian Tomlinson situation is making me angry for 2 reasons really. The first of these being the attitude of PC Harwood at the inquest who seems to think he is invincible now that criminal proceedings are not being pursued for manslaughter. He literally lied loads of times when being questioned, it was a total disgrace. I mean it is bad enough that it happened at all but to then lie about it in front of that poor mans family and friends is the final mark of disrespect. I am also angry that this inquest is using a jury of regular Joes to decide how this man died. If 2 coroners (ignoring the first one who seemingly plucked a cause of death out of thin air) have said he died of internal bleeding caused by a blow, then why is it even being looked at? Why has this policeman not been sacked and charged with manslaughter?
Anyway it got me onto thinking about how police should behave at marches / protests / demos as the worse this ConDem government gets then the more violence I predict at public demos. I don't know what the answer is and nobody seems to be able to see both sides of the argument. I was at the G20 on that day in 2009. I wanted to leave but I accepted being kettled as I understood it was for public protection. What I couldn't cope with however was that upon going to ask the police for help and advice, they were just plain rude. I ended up getting shoved by the crowd toward a police line, where I was punched, trodden on (loosing a shoe!) and covered in tear gas. I had only gone to ask a question and unfortunately the rough crowd behind me had surged forwards at that exact moment. And even though I was crying and telling this one officer I didn't want to push him, he just said it was tough and fought back against me. 
But then I know that the police do an excellent job most of the time, and that in such situations I think their training must be severely lacking. They seem to find it so hard to get a grip on the escalation of violence without resorting to it themselves. They get so mad at the protestors on the whole, violent or otherwise and just lump us all together, which in turn makes even the most mild mannered protestor angry and upset. So what is the answer? Well I don't know (or I would be the Chief of the Metropolitan police by now) but what I do know is that if a group of 100 or so "protestors" turn up at a march dressed all in black, with scarves etc covering their faces, then they ought to be removed immediately. They are ALWAYS the ones causing trouble, they chant the same ridiculous thing at every protest demonstrating their total lack of understanding and allegiance to the cause and are likely to cause damage, injury and police hostility towards the whole event. I think if you go to a peaceful protest with your face covered, you should be removed (not arrested) and only released once it is all over. They do this at football matches with risky people, and it can work. Why wait til the damage is done before acting? That is the equivalent of revising after an exam - a stupid waste of resources.