Let us start with what seems like an easier question: how long should a prison sentence be? The Criminal Justice Act 1991 confirmed that the basic rule is that the length should be commensurate with the seriousness of the offence committed (section 2(2)(a) of the 1991 Act, now section 80(2)(a) of the Powers of the Criminal Courts (Sentencing) Act 2000). Exceptionally a sentence may be longer, in order to protect the public from serious harm (section 2(2)(b) of the 1991 Act, now section 80(2)(b) of the Powers of the Criminal Courts (Sentencing) Act 2000). Discretionary life sentences fall into this latter category: the indeterminate sentence is imposed because of the risk that the offender is perceived to present to the public (see section 80(4) of the Act of 2000; Baker [2001] 1 Cr.App.R.(S) 551). These longer than commensurate life sentences are seen to fall into two parts: one, the “tariff” (though the Lord Chief Justice in a Practice Statement on 31 May 2002 stated that the term “minimum term” should now be used), commensurate with the seriousness of the offence, and the second for public protection. Because the factors which cause an offender to be dangerous may vary over time, the European Court of Human Rights has long held that those detained for such reasons are entitled to a review of that part of their sentence at regular intervals by a “court”. After years of reluctance the British Government agreed in the 1991 Act to create panels of the Parole Board, chaired by judges, to review whether post-tariff discretionary lifers are still dangerous. But the detention of those sentenced simply for “punishment” is justified by the original sentencing decision, even though their release date is fixed in accordance with a flexible and discretionary early release scheme.