either as a matter of principle in international law or as a matter of the language of article 1 of UNCAT. UK authorities 60. The appellant draws attention to the following passage in the speech of Lord Millett in Pinochet (No 3) as emphasising the governmental nature of the act of torture in article 1 UNCAT. “The definition of torture, both in the Convention and section 134, is in my opinion entirely inconsistent with the existence of a plea of immunity ratione materiae. The offence can be committed only by or at the instigation of or with the consent or acquiescence of a public official or other person acting in an official capacity. The official or governmental nature of the act, which forms the basis of the immunity, is an essential ingredient of the offence. No rational system of criminal justice can allow an immunity which is coextensive with the offence.” (at p 277D-E) So much is uncontroversial. What is more problematical is what constitutes acting in an official capacity, a matter on which, with one exception, the UK authorities provide little assistance. 61. The appellant relies on a line of authority concerning the relevant definition of torture for the purposes of immigration and asylum detention policy which, it is submitted, reveals a clear understanding that “person acting in an official capacity” in article 1 UNCAT refers to persons acting on behalf of the State. In R (EO) v Secretary of State for the Home Department [2013] EWHC 1236 (Admin), ACD 116 Burnett J concluded that “torture” in rule 35(3), Detention Centre Rules 2001 (SI 2001/238) (“DCR”) and in certain policy documents had a broader meaning than the UNCAT definition. It was not confined to acts of public officials or other persons acting in an official capacity or in which they were complicit or acquiesced. Subsequent to EO, the Secretary of State introduced statutory guidance entitled “Adults at Risk in Immigration Detention” (“AARSG”). The definition of “torture” for the purposes of rule 35 of DCR and the AARSG is set out in Detention Services Order, DSO 09/2016 which sets out the definition in article 1 UNCAT but adds: “It includes such acts carried out by terrorist groups exploiting instability or civil war to hold territory.” Page 29