Hundreds of riot police were deployed throughout central London on Tuesday as protests took place against next week’s G8 summit.
A building was occupied by demonstrators in Soho and there was a stand-off between protesters and police in Piccadilly near Fortnum & Mason.
The historic shop was targeted during protests against government cuts in 2011.
Metropolitan Police teams were out in force in a bid to keep the action under control and dramatically forced their way into the occupied building, a former police site, on Beak Street at lunchtime.
Television footage showed officers in climbing gear trying to secure the roof, bundling a protester who sprang on to the rooftop on to his front.
Around two dozen protesters gathered outside the BP headquarters in St James’s Square amid a heavy police presence.
Police said there was intelligence to suggest paint bombs and shields could be used against horses and officers in Westminster and the City of London.
Powers to stop and search in anticipation of violence and to require the removal of disguises were granted.
Scotland Yard also said that yesterday morning officers were given a search warrant for a building in Beak Street where it was believed protesters might have weapons.