44 AUAD v. BULGARIA JUDGMENT B. The Court’s assessment 127. The Court considers that this complaint is not manifestly ill-founded within the meaning of Article 35 § 3 (a) of the Convention or inadmissible on any other grounds. It must therefore be declared admissible. 128. On the merits, the Court reiterates that Article 5 § 1 (f), which permits the State to control the liberty of aliens in the immigration context, does not demand that detention be reasonably considered necessary, for example, to prevent the individual from committing an offence or fleeing. Any deprivation of liberty under the second limb of Article 5 § 1 (f) will be justified, however, only for as long as deportation or extradition proceedings are in progress. If such proceedings are not prosecuted with due diligence, the detention will cease to be permissible under that provision (see, among other authorities, Chahal, § 113; A. and Others v. the United Kingdom, § 164; Mikolenko v. Estonia, no. 10664/05, § 63, 8 October 2009; and Raza, § 72, all cited above). In other words, the length of the detention should not exceed that reasonably required for the purpose pursued (see Saadi v. the United Kingdom [GC], no. 13229/03, § 74 in fine, ECHR 2008-...). Indeed, a similar point was recently made by the ECJ in relation to Article 15 of Directive 2008/115/EC (see paragraphs 50 and 51 above). It should, however, be pointed out that unlike that provision, Article 5 § 1 (f) of the Convention does not contain maximum time-limits; the question whether the length of deportation proceedings could affect the lawfulness of detention under this provision thus depends solely on the particular circumstances of each case (see Osman v. the United Kingdom, no. 15933/89, Commission decision of 14 January 1991, unreported, and Gordyeyev v. Poland (dec.), nos. 43369/98 and 51777/99, 3 May 2005). 129. In the instant case, the applicant was detained under a decision issued by a competent authority in line with the applicable law, and action was being taken with a view to his deportation. His allegations in respect of the underlying expulsion order do not call into doubt the lawfulness of his detention (see Chahal, cited above, § 112; Slivenko v. Latvia [GC], no. 48321/99, § 146, ECHR 2003-X; and Sadaykov v. Bulgaria, no. 75157/01, § 21, 22 May 2008). 130. Therefore, the only issue is whether or not the authorities were sufficiently diligent in their efforts to deport the applicant. He remained in custody pending such deportation for exactly eighteen months, between 20 November 2009 and 19 May 2011 (see paragraphs 17 and 18 above). 131. In Raza (cited above, §§ 73-75), Bulgaria was found in breach of Article 5 § 1 in similar circumstances in respect of a detention lasting a little more than two and a half years. In the meantime, following legislative amendments intended to bring Bulgarian law into line with European Union law, the detention of deportees was subjected to strict time-limits of six, and in exceptional cases, eighteen months (see paragraph 44 above). As a result,