This section applies on an appeal against conviction where—
an appellant has been convicted of an offence to which he pleaded guilty,
if he had not so pleaded, he could on the indictment have pleaded, or been found, guilty of some other offence, and
it appears to the Court of Appeal that the plea of guilty indicates an admission by the appellant of facts which prove him guilty of the other offence.
The Court of Appeal may, instead of allowing or dismissing the appeal, substitute for the appellant's plea of guilty a plea of guilty of the other offence and pass such sentence in substitution for the sentence passed at the trial as may be authorised by law for the other offence, not being a sentence of greater severity.