72 A. AND OTHERS v. THE UNITED KINGDOM JUDGMENT the national authorities can be criticised, in the light of the evidence available to them at the time, for fearing that such an attack was “imminent”, in that an atrocity might be committed without warning at any time. The requirement of imminence cannot be interpreted so narrowly as to require a State to wait for disaster to strike before taking measures to deal with it. Moreover, the danger of a terrorist attack was, tragically, shown by the bombings and attempted bombings in London in July 2005 to have been very real. Since the purpose of Article 15 is to permit States to take derogating measures to protect their populations from future risks, the existence of the threat to the life of the nation must be assessed primarily with reference to those facts which were known at the time of the derogation. The Court is not precluded, however, from having regard to information which comes to light subsequently (see, mutatis mutandis, Vilvarajah and Others v. the United Kingdom, 30 October 1991, § 107(2), Series A no. 215). 178. While the United Nations Human Rights Committee has observed that measures derogating from the provisions of the International Covenant on Civil and Political Rights must be of “an exceptional and temporary nature” (see paragraph 110 above), the Court’s case-law has never, to date, explicitly incorporated the requirement that the emergency be temporary, although the question of the proportionality of the response may be linked to the duration of the emergency. Indeed, the cases cited above, relating to the security situation in Northern Ireland, demonstrate that it is possible for a “public emergency” within the meaning of Article 15 to continue for many years. The Court does not consider that derogating measures put in place in the immediate aftermath of the al-Qaeda attacks in the United States of America, and reviewed on an annual basis by Parliament, can be said to be invalid on the ground that they were not “temporary”. 179. The applicants’ argument that the life of the nation was not threatened is principally founded on the dissenting opinion of Lord Hoffman, who interpreted the words as requiring a threat to the organised life of the community which went beyond a threat of serious physical damage and loss of life. It had, in his view, to threaten “our institutions of government or our existence as a civil community” (see paragraph 18 above). However, the Court has in previous cases been prepared to take into account a much broader range of factors in determining the nature and degree of the actual or imminent threat to the “nation” and has in the past concluded that emergency situations have existed even though the institutions of the State did not appear to be imperilled to the extent envisaged by Lord Hoffman. 180. As previously stated, the national authorities enjoy a wide margin of appreciation under Article 15 in assessing whether the life of their nation is threatened by a public emergency. While it is striking that the United Kingdom was the only Convention State to have lodged a derogation in