20.— (1) It shall be a defence (to be known, and in this section referred to, as the “defence of honest opinion”) to a defamation action for the defendant to prove that, in the case of a statement consisting of an opinion, the opinion was honestly held.

(2) Subject to subsection (3), an opinion is honestly held, for the purposes of this section, if—

(a) at the time of the publication of the statement, the defendant believed in the truth of the opinion or, where the defendant is not the author of the opinion, believed that the author believed it to be true,

(b) (i) the opinion was based on allegations of fact—

(I) specified in the statement containing the opinion, or

(II) referred to in that statement, that were known, or might reasonably be expected to have been known, by the persons to whom the statement was published,

or

(ii) the opinion was based on allegations of fact to which—

(I) the defence of absolute privilege, or

(II) the defence of qualified privilege,

would apply if a defamation action were brought in respect of such allegations,

and

(c) the opinion related to a matter of public interest.

(3) (a) The defence of honest opinion shall fail, if the opinion concerned is based on allegations of fact to which subsection (2) (b) (i) applies, unless—

(i) the defendant proves the truth of those allegations, or

(ii) where the defendant does not prove the truth of all of those allegations, the opinion is honestly held having regard to the allegations of fact the truth of which are proved.

(b) The defence of honest opinion shall fail, if the opinion concerned is based on allegations of fact to which subsection (2) (b) (ii) applies, unless—

(i) the defendant proves the truth of those allegations, or

(ii) where the defendant does not prove the truth of those allegations—

(I) the opinion could not reasonably be understood as implying that those allegations were true, and

(II) at the time of the publication of the opinion, the defendant did not know or could not reasonably have been expected to know that those allegations were untrue.

(4) Where a defamatory statement consisting of an opinion is published jointly by a person (“ first-mentioned person ”) and another person (“ joint publisher ”), the first-mentioned person shall not fail in pleading the defence of honest opinion in a subsequent defamation action brought in respect of that statement by reason only of that opinion not being honestly held by the joint publisher, unless the first-mentioned person was at the time of publication vicariously liable for the acts or omissions, from which the cause of action in respect of that statement accrued, of the joint publisher.