No act of a person which, but for this section would constitute an offence, is an offence if—
(a) it was done in order to avoid consequences which could not otherwise be avoided and which if they had occurred would have inflicted upon him or her or another person whom he or she was bound to protect inevitable or irreparable harm or damage;
(b) it was no more than was reasonably necessary for that purpose; and
(c) the harm inflicted by it was not disproportionate to the danger avoided.