13.—(1) This Article applies where—
(a)a person is convicted on indictment of a serious offence committed after the commencement of this Article; and
(b)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.
(2) If—
(a)the offence is one in respect of which the offender would apart from this Article be liable to a life sentence, an
(b)the court is of the opinion that the seriousness of the offence, or of the offence and one or more offences associated with it, is such as to justify the imposition of such a sentence,
the court shall impose a life sentence.
(3) If, in a case not falling within paragraph (2), the court considers that an extended custodial sentence would not be adequate for the purpose of protecting the public from serious harm occasioned by the commission by the offender of further specified offences, the court shall—
(a)impose an indeterminate custodial sentence; and
(b)specify a period of at least 2 years as the minimum period for the purposes of Article 18, being such period as the court considers appropriate to satisfy the requirements of retribution and deterrence having regard to the seriousness of the offence, or of the combination of the offence and one or more offences associated with it.
(4) An indeterminate custodial sentence is—
(a)where the offender is aged 21 or over, a sentence of imprisonment for an indeterminate period,
(b)where the offender is under the age of 21, a sentence of detention for an indeterminate period at such place and under such conditions as the Secretary of State may direct,
subject (in either case) to the provisions of this Part as to the release of prisoners and duration of licences.
(5) A person detained pursuant to the directions of the Secretary of State under paragraph (4)(b) shall while so detained be in legal custody.
(6) An offence the sentence for which is imposed under this Article is not to be regarded as an offence the sentence for which is fixed by law.
(7) Remission shall not be granted under prison rules to the offender in respect of a sentence imposed under this Article.