The issue then becomes whether the officers were justi-
fied in taking the steps that they did to arrest the respondent
and remove him from the area of conflict in order to avoid
a breach, or potential breach, of the peace. Doherty J.A. defined
a breach of the peace as follows in Brown, at para. 73:
A breach of the peace contemplates an act or actions which result in actual
or threatened harm to someone. Actions which amount to a breach of the
peace may or may not be unlawful standing alone. Thus, in Percy v. D.P.P.,
 3 All E.R. 124 (at 131 (Q.B.), Collins J. observed:
The conduct in question does not itself have to be disorderly or a breach
of the criminal law. It is sufficient if its natural consequence would, if
persisted in, be to provoke others to violence, and so some actual dan-
ger to the peace is established.
 Doherty J.A. added that the apprehended breach of the
peace must be imminent and the risk of a breach must be sub-
stantial. He concluded, at para. 74:
To properly invoke either power, the police officer must have reasonable
grounds for believing that the anticipated conduct, be it a breach of the
peace or the commission of an indictable offence, will likely occur if the per-
son is not detained.
 In R. v. MacDonald,  1 S.C.R. 37,  S.C.J.
No. 3, 2014 SCC 3, LeBel J. commented on what form of police
conduct will be a justifiable exercise of the common law power,
at para. 36:
Thus, for the infringement to be justified, the police action must be reasona-
bly necessary for the carrying out of the particular duty in light of all the
(Citations omitted; emphasis in original)
 In determining whether the police action is reasonably
necessary, LeBel J. referred to the Dedman and Mann lines of
cases as defining the limits on the exercise of the police power.2
Those limits involve the importance of the duty; the necessity of
the infringement arising from the duty; and the extent of the
resulting infringement. In terms of the importance of the duty,
LeBel J. said, at para. 39:
No one can reasonably dispute that the duty to protect life and safety is
of the utmost importance to the public good and that, in some circum-
stances, some interference with individual liberty is necessary to carry
out that duty.
2 R. v. Dedman,  2 S.C.R. 2,  S.C.J. No. 45; Mann, supra.