A. AND OTHERS v. THE UNITED KINGDOM JUDGMENT 63 were in negotiation with the governments of Algeria and Jordan, with a view to entering into memoranda of understanding that the applicants who were nationals of those countries would not be ill-treated if returned. 148. The Government relied on the principle of fair balance, which underlies the whole Convention, and reasoned that sub-paragraph (f) of Article 5 § 1 had to be interpreted so as to strike a balance between the interests of the individual and the interests of the State in protecting its population from malevolent aliens. Detention struck that balance by advancing the legitimate aim of the State to secure the protection of the population without sacrificing the predominant interest of the alien to avoid being returned to a place where he faced torture or death. The fair balance was further preserved by providing the alien with adequate safeguards against the arbitrary exercise of the detention powers in national security cases. 149. In the alternative, the detention of the applicants was not in breach of the Convention because of the derogation under Article 15. There was a public emergency threatening the life of the nation at the relevant time. That assessment was subjected to full scrutiny by the domestic courts. The evidence in support, both open and closed, was examined by SIAC in detail, with the benefit of oral hearings at which witnesses were cross-examined. SIAC unanimously upheld the Government’s assessment, as did the unanimous Court of Appeal and eight of the nine judges in the House of Lords. In the light of the margin of appreciation to be afforded to the national authorities on this question, there was no proper basis on which the Court could reach a different conclusion. 150. The Government explained that they accorded very great respect to the House of Lords’ decision and declaration of incompatibility and that they had repealed the offending legislation. Nonetheless, when the decision was made to refer the case to the Grand Chamber, they decided that it was necessary to challenge the House of Lords’ reasoning and conclusions, bearing in mind the wide constitutional importance of the issue and the ongoing need for Contracting States to have clear guidance from the Grand Chamber as to the measures they might legitimately take to try to prevent the terrorist threat from materialising. They submitted that the House of Lords had erred in affording the State too narrow a margin of appreciation in assessing what measures were strictly necessary; in this connection it was relevant to note that Part 4 of the 2001 Act was not only the product of the judgment of the Government but was also the subject of debate in Parliament. Furthermore, the domestic courts had examined the legislation in the abstract, rather than considering the applicants’ concrete cases, including the impossibility of removing them, the threat each posed to national security, the inadequacy of enhanced surveillance or other controls short of detention and the procedural safeguards afforded to each applicant.