This section applies where the court dealing with an offender is required by section 282B to impose a serious terrorism sentence of imprisonment under section 282A.
The appropriate custodial term is—
14 years, or
if longer, the term of imprisonment that would be imposed in respect of the offence in compliance with section 231(2) (length of discretionary custodial sentences) if the court did not impose a serious terrorism sentence of imprisonment (or an extended sentence or a sentence under section 278).
The extension period must—
be at least 7 years, and
not exceed 25 years.