For at least a century and a quarter one of the most settled and invariable maxims of the criminal law, founded upon a decision of 15 judges in the Court for Crown Cases Reserved (Prince (1875) 2 C.C.R. 154; see, also, Robins (1844) 1 C. & K. 456), has been that the prosecution did not have to prove fault on the defendant’s part in respect of the element of age in statutory offences created for the protection of the young. Many statutes have been drafted (or amended), and thousands upon thousands of defendants have been convicted, on this basis. But no longer. For the Appellate Committee has decreed, without giving any reasons for doing so-there is just a bare assertion (B. v. D.P.P. [2000] A.C. 428, reversing a unanimous decision of a strong Divisional Court: [1998] 4 All E.R. 265)—that “an age-related ingredient of a statutory offence stands on no different footing from any other ingredient”, and that proof of fault (in the shape of the absence of a belief-reasonable or unreasonable—that the child is above the proscribed age) is required unless excluded by Parliament either expressly or by “necessary implication, … [that is, by] an implication which is compellingly clear” (Lord Nicholls). “Such an implication”, we are told, “may be found in the language used, the nature of the offence, the mischief sought to be prevented, and any other circumstances which may assist in determining what intention is to be attributed to Parliament when creating the offence” (ibid.). This is, of course, none other than the all too depressingly familiar litany of vague, overlapping criteria which from time out of mind has signally failed to compel from the judges predictable answers to the question whether, when Parliament has been silent on the point, a person must, if she is to be convicted of a given offence, be presumed to have been at fault in respect of all, or some, of its external elements. The reference to a silent legislature’s intention is to a fiction—a mere rhetorical device. There is, as everyone knows, only one sure and compelling guide: the express provision of a no-fault defence logically precludes a requirement to prove fault in regard to the matter to which it refers.