Sch 20B para 20
Paragraphs 21 and 22 apply where a person (“P”) is serving two or more sentences of imprisonment imposed on or after 1 October 1992 and— (a) the sentences were passed on the same occasion, or (b) where they were passed on different occasions, the person has not been released under Part 2 of the 1991 Act or under this Chapter at any time during the period beginning with the first and ending with the last of those occasions.