Admissibility in evidence, in mitigation of damages in action for defamation, of apology

In any action for defamation, it shall be lawful for the defendant (after notice in writing of his intentions to do so, duly given to the plaintiff within a reasonable time before the trial of the action) to give in evidence, in mitigation of damages, that he made or offered an apology to the plaintiff for 5 the defamation before the commencement of the action, or as soon afterwards as he had an opportunity of doing so, in case the action has been commenced before there was an opportunity of making or offering apology.