If you are going to any G20 demo please make sure you have a camera + good batteries and spares (also spare tape, memory cards whatever). Stills are better than nothing, video with sound is best. Get a good mix of close ups of action and longer shots to show the context, both are essential. When it’s the fuzz’s word against yours they will always get away with it unless there is documentary evidence plus it will make it untenable for corporate media to whitewash police violence if it is all over the web. By most signs the fuzz plan on using a great deal of violence to protect the ruling classes pursuit of Shock Doctrine ‘reforms’. Good luck, take care!