- 18 58. It was decided that each delegation should agree upon a Head of the delegation, in consultation with the CPT's Bureau (cf. Rule 37, paragraph 3). The Head of the delegation is responsible for the actual conduct of the visit. In particular, he or she is in charge of relations with the national authorities of the country visited and organises, as well as oversees, the drafting of the delegation's report. 59. As regards experts, the CPT decided as a first step to request the Secretariat to prepare a tentative list of experts, on the basis of suggestions made by Committee members and of names already known to the Secretariat or brought to its attention by reliable sources. Secondly, the CPT decided that experts should be appointed on an ad hoc basis, i.e. in relation to a particular visit: no-one should receive an on-going appointment as an expert of the CPT. Thirdly, it was decided that, during a visit, individual experts should not be allowed to conduct on their own discussions with national authorities; on the other hand an individual expert might interview detainees on his own, provided that he had been expressly authorised to do so by the Head of the visiting delegation. 60. The CPT decided that each visiting delegation could divide into sub-groups, each of the groups to include a medical doctor whenever possible and appropriate. In fact, all the delegations that carried out visits in 1990 frequently split into two or even three sub-groups. Indeed, there is is often no need for the whole delegation to undertake a visit to a specific place or to be present at discussions with national authorities or relevant non-governmental organisations. It should be added that whenever the whole of a CPT delegation does visit a place of detention (e.g. a large prison), it invariably divides into sub-groups when working within the place concerned. In this way the effectiveness and thoroughness of the visit are greatly enhanced. Regular meetings of the whole delegation in the course of and/or at the end of the day ensure that there is due coordination of the activities of sub-groups. c) Length of visits 61. The CPT decided that, at least in 1990, visits to small countries should last roughly one week while those to large countries should last up to two weeks. The CPT's visiting delegations abided by this decision (see paragraph 54). d) Places visited 62. The choice of the actual places of detention to be visited in each of the countries selected is made by the delegation, on the basis of the information available to it. The national member takes part in the first meeting that the delegation holds to prepare its visit and may inter alia suggest places and institutions to be visited. That is in principle where the national member's participation ends. However, he or she remains at the disposal of the delegation in the event of the latter requiring supplementary information or advice. Of course, once in the country visited, the delegation may decide on the spot to visit places of detention other than these originally selected and notified to the national authorities (see Article 8, paragraph 1, of the Convention and paragraph 58 of the Explanatory Report).