this court to substitute its findings for those of the trial judge on
this or any other point of factual disagreement.
 In my view, my colleague misconstrues and so minimizes
the necessity requirement. He acknowledges that the police
could have instituted a buffer zone between Mr. Fleming and the
protesters and could have called for backup rather than arrest-
ing him, but concludes, at para. 57:
There was no need to institute a buffer zone if the matter could be addressed
by removing the respondent as the source of the friction. Further, there is no
reason to believe that a buffer zone of six or seven officers against eight to
ten rushing protestors (with others available to join that group) would have
been effective or whether it would have simply resulted in a larger confron-
tation. Similarly, there was no reason to call for back-up, and run the risk
of inflaming tensions by such a show of force, if, again, the matter could
be addressed by removing the respondent.
 Thus, in the face of concern that illegal violence might
occur, my colleague sanctions the removal and arrest of Mr.
Fleming — whose exercise of Charter rights broke no laws — as
a first option in preserving the peace rather than a last resort.
 This turns the concept of necessity on its head. The
question is not whether arresting and removing someone might
prevent a breach of the peace; the answer to that question will
almost always be yes. The question is whether the extraordinary
step of a pre-emptive arrest was necessary because a breach of
the peace was imminent and the risk that it would occur was
substantial, and that breach could not be reasonably prevented
by some alternative police action. In this regard, I note that
the trial judge found, at pp. 54-65, that “[t]here were many other
less invasive options that could have been implemented to
defuse the situation”.
 The trial judge concluded, at p. 43, that there was “no
evidence to support a finding that there was a reasonable basis
for the O.P.P officers to believe there was an imminent risk
that a breach of the peace would occur, or that the risk that
it would occur was substantial”. Nordheimer J.A. rejects this
conclusion, but he does not analyze the requirements of imminence or substantiality, nor does he explain why the trial
judge’s interpretation and application of the test was wrong.
His conclusion, that the police had reasonable grounds to
believe that there was an imminent risk to the public peace
and a substantial risk of harm to Mr. Fleming, appears to flow
from his view that the police are entitled to deference in such
matters. He notes, at para. 57: