application was being considered. In these circumstances it could not be said that Mr Assenov had been denied a trial within a reasonable time. 152. The Commission, attaching particular importance to the fact that between September 1995 and September 1996 the preliminary investigation had been practically dormant, found that Mr Assenov, who had then been detained on remand for over twenty-three months, had been denied a trial within a reasonable time. The applicant agreed with this conclusion. 153. The Court observes that the period to be taken into consideration commenced on 27 July 1995, when Mr Assenov was arrested, and continued until an unspecified day in July 1997, when he was convicted and sentenced in respect of four robberies (see paragraphs 33 and 48 above). His pre-trial detention therefore lasted approximately two years. 154. The Court reiterates that it falls in the first place to the national judicial authorities to ensure that the pre-trial detention of an accused person does not exceed a reasonable time. To this end, they must examine all the circumstances arguing for and against the existence of a genuine requirement of public interest justifying, with due regard to the principle of the presumption of innocence, a departure from the rule of respect for individual liberty and set these out in their decisions on the applications for release. It is essentially on the basis of the reasons given in these decisions and of the true facts mentioned by the detainee in his applications for release and his appeals that the Court is called upon to decide whether or not there has been a violation of Article 5 § 3. The persistence of reasonable suspicion that the person arrested has committed an offence is a condition sine qua non for the validity of the continued detention, but, after a certain lapse of time, it no longer suffices: the Court must then establish whether the other grounds cited by the judicial authorities continued to justify the deprivation of liberty. Where such grounds were “relevant” and “sufficient”, the Court must also ascertain whether the competent national authorities displayed “special diligence” in the conduct of the proceedings (see the Toth v. Austria judgment of 12 December 1991, Series A no. 224, p. 18, § 67). 155. The Court recalls that on the two occasions when the legality of Mr Assenov’s detention was reviewed by a court, his release was refused on the grounds that he was charged with a number of serious crimes and that his criminal activity had been persistent, giving rise to a danger that he would reoffend if released (see paragraphs 38 and 47 above). 156. The Court notes that on 28 July 1995 Mr Assenov was charged with sixteen or more burglaries and robberies, the latter involving some violence (see paragraph 33 above). Although he had first been questioned in connection with the investigation into this series of thefts in January 1995 (see paragraph 32 above), a number of the offences with which he was charged were committed subsequently; the last robbery having taken place on 24 July, three days before his arrest.