The Act Commentary on Sections Part 4 - Sentencing Section 126: Determination of tariffs etc
586.This section applies where a court is imposing an indeterminate sentence such as a mandatory life sentence, discretionary life sentence, imprisonment for public protection sentence or an extended sentence for certain violent and sexual offences. In these cases, the court is required to follow the guidelines specifying a sentence range when determining the notional determinate term for the purpose of setting a tariff for the indeterminate sentence.