A decision to contain a substantial crowd of demonstrators, whose behaviour did not of itself justify containment, was justifiable on the ground that containment was the least drastic way of preventing what the police officer responsible for the decision reasonably apprehended would otherwise be imminent and serious breaches of the peace.

CA (Civ Div) (Lord Neuberger (MR), Hughes LJ, Sullivan LJ) 19/1/2012
[2012] EWCA Civ 12