If D does an act that is intended to restrain P, it is not an act to which section 5 applies unless two further conditions are satisfied.
The first condition is that D reasonably believes that it is necessary to do the act in order to prevent harm to P.
The second is that the act is a proportionate response to—
the likelihood of P's suffering harm, and
the seriousness of that harm.
For the purposes of this section D restrains P if he—
uses, or threatens to use, force to secure the doing of an act which P resists, or
restricts P's liberty of movement, whether or not P resists.
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Section 5 does not authorise a person to do an act which conflicts with a decision made, within the scope of his authority and in accordance with this Part, by—
a donee of a lasting power of attorney granted by P, or
a deputy appointed for P by the court.
But nothing in subsection (6) stops a person—
providing life-sustaining treatment, or
doing any act which he reasonably believes to be necessary to prevent a serious deterioration in P's condition,
while a decision as respects any relevant issue is sought from the court.