–6– Regrettably, in many Council of Europe member states, it remains the case that juveniles on remand in particular are frequently held in prisons for adults. The CPT acknowledges that, in such cases, juveniles are nowadays usually accommodated separately from adults, often in a designated unit. In addition, significant improvements have been observed in recent years in terms of material conditions in juvenile units. However, in a number of countries, the regime offered to juvenile remand prisoners held in adult prisons still leaves much to be desired, especially in remand establishments which usually accommodate only very small numbers of juveniles (in particular female juveniles). On several occasions, the CPT observed that only one juvenile was being held on remand in a given establishment or unit. In this regard, the Committee acknowledges that there may be an argument in favour of juveniles participating in out-of-cell activities with suitable adult inmates, on the strict condition that there is appropriate supervision by staff. This also has the benefit of avoiding a situation of de facto solitary confinement of the juveniles concerned. 68. As repeatedly stated by the CPT in the past, although a lack of purposeful activity is detrimental for any prisoner, it is especially harmful for juveniles, who have a particular need for physical activity and intellectual stimulation. Juveniles in remand detention should be offered a full programme of out-of-cell activities suited to their age, such as education, sport, vocational training and recreational activities. Physical education should constitute an important part of that programme. Juveniles should also be offered at least two hours of outdoor exercise every day, from the moment they arrive at a detention establishment. As already mentioned in paragraph 58 regarding remand prisoners in general, the longer the period of detention on remand, the more varied should be the activities on offer. 4. Remand detention in law enforcement establishments 69. The CPT has serious reservations about the practice observed in a number of countries of holding persons remanded in custody by courts in a law enforcement establishment well beyond the statutory time limit of police custody, pending their transfer to a remand prison, or of returning persons placed in a remand prison to a law enforcement establishment for the purpose of investigative actions. Such periods of stay may last several days or weeks and, on occasion, even longer. Usually, persons remanded in custody remain in a law enforcement establishment after their court hearing or are returned to the law enforcement establishment from a prison for the purpose of investigative actions, at the request of the law enforcement official who is responsible for the criminal investigation. In some cases, delays in transferring persons remanded in custody to a remand prison are explained by logistical obstacles in arranging escorts or by the lack of space for accommodation in the remand prison (due to severe overcrowding). 70. The CPT recalls that, as a matter of principle, remand prisoners should not be held in law enforcement establishments;15 such facilities are not designed for lengthy periods of stay. Moreover, prolonged detention on the premises of law enforcement agencies increases the risk of intimidation and ill-treatment by law enforcement officials dealing with the criminal investigation against the person concerned. Therefore, persons remanded in custody should always be promptly transferred to a prison. Further, the return of remand prisoners to detention facilities of law enforcement agencies should be sought and authorised only very exceptionally and when it is absolutely unavoidable, for specific reasons and for the shortest possible time. Such a return should in each case be subject to the express authorisation of a prosecutor or judge. As a rule, the prisoners concerned should not be held 15 See also Rule 10.2 of the European Prison Rules.