This section applies where a court is dealing with an offender for an offence where—
the offender is aged 18 or over but under 21 when convicted of the offence,
the offence is a Schedule 19 offence (see section 307), and
the court is of the opinion that there is a significant risk to members of the public of serious harm occasioned by the commission by the offender of further specified offences (see sections 306(1) and 308).
The pre-sentence report requirements (see section 30) apply to the court in relation to forming the opinion mentioned in subsection (1)(c).
If the court considers that the seriousness of—
the offence, or
the offence and one or more offences associated with it,
is such as to justify the imposition of a sentence of custody for life, the court must impose a sentence of custody for life under section 272.
An offence the sentence for which is imposed under this section is not to be regarded as an offence the sentence for which is fixed by law.