267Extended sentence of detention in a young offender institution: availability
(1)An extended sentence of detention in a young offender institution is available in respect of an offence where—
(a)the offence is a specified offence (see section 306(1)),
(b)the offender is aged at least 18 but under 21 when convicted of the offence,
(c)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 section 308),
(d)the court is not required by section 273 or 274 to impose a sentence of custody for life, and
(e)the earlier offence condition or the 4 year term condition is met.
(2)The pre-sentence report requirements (see section 30) apply to the court in relation to forming the opinion mentioned in subsection (1)(c).
(3)The earlier offence condition is that, when the offence was committed, the offender had been convicted of an offence listed in Schedule 14.
(4)The 4 year term condition is that, if the court were to impose an extended sentence, the term that it would specify as the appropriate custodial term (see section 268) would be at least 4 years.