" ... that the behaviour that caused a constable to believe that a breach of the peace had or would occur had to be related to violence and such a breach occurred whenever harm was actually done or likely to be done to a person or in his presence to his property or a person was put in fear of being so harmed through an assault, affray, riot, unlawful assembly or other disturbance."
"We hold that there is a power of arrest for breach of the peace where (1) a breach of the peace is committed in the presence of the person making the arrest ... (2) the arrestor reasonably believes that such a breach will be committed in the immediate future by the person arrested although he has not yet committed any breach ..."
"The common law power of a police constable to arrest, where no actual breach of the peace has occurred but where he apprehended that such a breach might be caused by apparently lawful conduct, was exceptional and should be exercised by him only in the clearest circumstances when he was satisfied on reasonable grounds that a breach of the peace was about to occur or was imminent. There had to be a sufficiently real and present threat to the peace to justify the extreme step of depriving of his liberty the citizen who was not at the time acting unlawfully."
"The test to determine whether the police officer's action was reasonable was an objective one, in the sense that it was for the courts to decide, not whether the view taken by that officer fell within the broad band of rational decisions but whether, in the light of what he knew and perceived at the time, the court was satisfied that it was reasonable to fear an imminent breach of the peace and that reasonableness had to be evaluated without the qualifications of hindsight."
" ... agitation or excitement, including hysterical waving of a handbag ... in front of a police officer interviewing a member of the public in the street did not constitute a breach of the peace to justify a lawful arrest."