Terrorism (High Risk Offenders) Act 2017

An interim detention order in respect of an eligible offender commences on the day fixed in the order for its commencement (or, if no such day is fixed, as soon as it is made) and expires—

at the end of such period (not exceeding 28 days from the day on which it commences) as is specified in the order, or

if the order is suspended for any period—the period specified in paragraph (a) plus each period during which the order is suspended, or

on the commencement of an extended supervision order made in respect of the offender.

An eligible offender’s custody under an interim detention order is suspended during any period the offender is in lawful custody, whether under this or any other Act or law.

An interim detention order may be renewed from time to time, but not so as to provide for the detention of the eligible offender under such an order for periods totalling more than 3 months.