Before the event Commander Simon O'Brien said that the capital would see " almost unprecedented level of activity " of protest activity with seven officially notified demonstrations and possibly many more they do n't know about . Scotland Yard described the G20 policing plan as one of the largest , most challenging and complicated public order operations it has ever devised . They said that the level and style of activity on the internet suggested a re-emergence of groups with similar aims to the anti-globalisation protesters who turned to violence in 2000 and 2001 . They said they were determined to avoid the violent scenes of the 2001 G8 in Genoa in which one protester was killed and hundreds more injured . In the days leading up to the summit , the Metropolitan police warned protest groups that the protests on 1 April would be " very violent " and that they were " up for it , and up to it " in the event of trouble
G8 in Genoa
27th G8 summit
2009 G20 London summit protests