What is the test for recklessness with the truth?

At paragraph 96, the court notes that recklessness with the truth will amount to actual malice, but mere carelessness will not. The court then (in paragraph 97) cited with approval the following statement of Lord Diplock in Horrocks v. Lowe: …what is required on the part of the defamer to entitle him to the protection of the privilege is positive belief in the truth of what he published or, as it is generally though tautologously termed, “honest belief.” If he publishes untrue defamatory matter recklessly, without considering or caring whether it be true or not, he is in this, as in other branches of the law treated as if he knew it to be false. But indifference to the truth of what he publishes is not to be equated with carelessness, impulsiveness or irrationality in arriving at a positive belief that it is true. …But despite the imperfection of the mental process by which the belief is arrived at it may still be “honest,” that is, a positive belief that the conclusions they have reached are true. The law demands no more.