Sentence on offender already sentenced for another offence
397. When a person already undergoing a sentence of imprisonment, or transportation, is sentenced to imprisonment, or transportation, such imprisonment, or transportation shall commence at the expiration of the imprisonment, or transportation to which he has been previously sentenced, unless the Court directs that the subsequent sentence shall run concurrently with such previous sentence:
Provided that, if he is undergoing a sentence of imprisonment, and the sentence on such subsequent conviction is one of transportation, the Court may, in its discretion, direct that the latter sentence shall commence immediately, or at the expiration of the imprisonment to which he has been previously sentenced:
Provided, further, that where a person who has been sentenced to imprisonment by an order under section 123 in default of furnishing security is, whilst undergoing such sentence, sentenced to imprisonment for an offence committed prior to the making of such order, the latter sentence shall commence immediately.