This section applies where—
(a) two or more related sentences are passed,
(b) the Court of Appeal allow an appeal against conviction in respect of one or more of the offences for which the sentences were passed ("the related offences"), but
(c) the appellant remains convicted of one or more of those offences.
Except as provided by subsection (3) below, the Court may in respect of any related offence of which the appellant remains convicted pass such sentence, in substitution for any sentence passed thereon at the trial, as they think proper and is authorised by law ... .
The Court shall not under this section pass any sentence such that the appellant's sentence (taken as a whole) for all the related offences of which he remains convicted will, in consequence of the appeal, be of greater severity than the sentence (taken as a whole) which was passed at the trial for all the related offences.
For the purposes of subsection (1)(a), two or more sentences are related if—
(a) they are passed on the same day,
(b) they are passed on different days but the court in passing any one of them states that it is treating that one together with the other or others as substantially one sentence, or
(c) they are passed on different days but in respect of counts on the same indictment.
Where—
(a) two or more sentences are related to each other by virtue of subsection (4)(a) or (b), and
(b) any one or more of those sentences is related to one or more other sentences by virtue of subsection (4)(c),
all the sentences are to be treated as related for the purposes of subsection (1)(a).