78 A. AND OTHERS v. THE UNITED KINGDOM JUDGMENT limited role they were able to play in closed hearings given the absence of effective instructions from those they represented. B. The Court’s assessment 1. Admissibility 200. The Court notes that Article 5 § 4 guarantees a right to “everyone who is deprived of his liberty by arrest or detention” to bring proceedings to test the legality of the detention and to obtain release if the detention is found to be unlawful. Since the second and fourth applicants were already at liberty, having elected to travel to Morocco and France respectively, by the time the various proceedings to determine the lawfulness of the detention under the 2001 Act were commenced, it follows that these two applicants’ complaints under Article 5 § 4 are manifestly ill-founded within the meaning of Article 35 § 3 of the Convention (see Fox, Campbell and Hartley v. the United Kingdom, 30 August 1990, § 45, Series A no. 182) and must be declared inadmissible. 201. The Court considers that the other applicants’ complaints under this provision raise complex issues of law and fact, the determination of which should depend on an examination of the merits. It concludes, therefore, that this part of the application is not manifestly ill-founded within the meaning of Article 35 § 3 of the Convention. No other ground of inadmissibility has been raised and it must be declared admissible. 2. The merits (a) The principles arising from the case-law 202. Article 5 § 4 provides a lex specialis in relation to the more general requirements of Article 13 (see Chahal, cited above, § 126). It entitles an arrested or detained person to institute proceedings bearing on the procedural and substantive conditions which are essential for the “lawfulness” of his or her deprivation of liberty. The notion of “lawfulness” under Article 5 § 4 has the same meaning as in § 1, so that the arrested or detained person is entitled to a review of the “lawfulness” of his detention in the light not only of the requirements of domestic law but also of the Convention, the general principles embodied therein and the aim of the restrictions permitted by Article 5 § 1. Article 5 § 4 does not guarantee a right to judicial review of such a scope as to empower the court, on all aspects of the case including questions of pure expediency, to substitute its own discretion for that of the decision-making authority. The review should, however, be wide enough to bear on those conditions which are essential for the “lawful” detention of a person according to Article 5 § 1 (see E. v.