(1) This part applies to a sentence of imprisonment (a primary sentence ) imposed by a court on an offender if—
(a) any of the following apply in relation to the offender:
(i) when the primary sentence is imposed, the offender is serving another sentence of imprisonment (an existing sentence );
(ii) the offender has been sentenced to another sentence of imprisonment (also an existing sentence ) but, when the primary sentence is imposed, the other sentence has not yet started;
(iii) the offender is sentenced to another sentence of imprisonment (also an existing sentence ) in the same proceeding; and
(b) the existing sentence is for an offence against a territory law; and
(c) the primary sentence is not fully suspended.
(2) In this section:
"sentence of imprisonment"—
(a) does not include any nonparole period that has been set for the primary sentence; but
(b) includes an order committing a young person to an institution under the Children and Young People Act 1999 , section 96 (1) (k) or (l).