Section 45 defines libel: a false and unprivileged publication by writing, printing, picture, effigy or other fixed representation to the eye, which exposes any person to hatred, contempt, ridicule or obloquy, or which causes them to be shunned or avoided, or which has a tendency to injure them in their occupation. Four conditions have to be met and every one of them is a place a claim fails.
False. Truth is not a defence bolted on afterwards — falsity is written into the definition, so a statement that is substantially true is not libel however damaging or maliciously intended. Unprivileged. The privileges in § 47 are likewise part of the definition rather than an excuse, which is why statements in court papers, in official proceedings and in certain communications between interested persons are not libel at all. Published by a fixed representation to the eye. The section is not confined to newspapers: a post, a review, a group message, a sign, a photograph or a drawing all qualify, and publication means communication to someone other than the person defamed.
And the effect: hatred, contempt, ridicule, obloquy, being shunned or avoided, or a tendency to injure in occupation. That last limb is why accusations about someone's work — dishonesty, incompetence, misconduct in a trade — are the commonest libel claims. What the section does not include is anything about opinion, about damages, or about who has to prove what: those come from case law and from other sections, including the retraction and damages rules in § 48a. Whether a particular statement is one of fact rather than opinion, and whether a privilege applies, are the two questions that decide most of these disputes, and both belong with a lawyer.