CAT/OP/3/Rev.2 necessary or appropriate to do so and in such cases, each decision shall be communicated to the members as soon as possible, taking due account of the requirement of confidentiality. The Bureau shall report to the Subcommittee at each session on any decisions or actions of an urgent or delegated nature taken on behalf of the Subcommittee since its previous session. 2. The Bureau shall meet as required in order to fulfil its obligations and the mandate of the Subcommittee. Rule 19 Powers and duties of the Chair and Vice-Chairs 1. The Chair shall exercise his or her functions under the authority of the Subcommittee. In accordance with the present rules of procedure, the Chair shall ensure the orderly conduct of the meetings of the Subcommittee, including observance of the present rules of procedure. 2. The Chair shall represent the Subcommittee at United Nations and other official meetings. If the Chair is unable to represent the Subcommittee at a meeting, he or she may designate one of the Vice-Chairs to represent the Subcommittee. If no Vice-Chair is available, a member of the Subcommittee may be designated by the Bureau to represent the Subcommittee. 3. The Vice-Chairs and other members of the Subcommittee shall undertake such specific functions as are entrusted to them by the Chair. Rule 20 Acting Chair and Vice-Chairs 1. If, during a session, the Chair is unable to be present at a meeting or any part thereof, the Chair shall designate a Vice-Chair to act in his or her place. 2. If the Chair and Vice-Chairs are simultaneously unable to carry out their duties, or if none have been elected or are otherwise unavailable, the Subcommittee shall entrust such duties to any member of the Subcommittee until such time as the Chair or Vice-Chairs become available, assume their functions or are elected. The Secretary-General may, if necessary and in consultation with the Subcommittee, call a meeting for that purpose. 3. If it is proposed that more than one member of the Subcommittee undertake the functions of the Chair temporarily and a consensus is not reached, the member who is most senior in terms of Subcommittee membership shall preside as Acting Chair. In cases in which any two or more proposed members have the same length of service in the Subcommittee and a consensus is not reached, then the most senior member by age shall preside as Acting Chair. 4. Any member of the Subcommittee acting as Chair shall have the same powers and duties as the Chair. 5. In the event that the Chair or any Vice-Chair is no longer a member of the Subcommittee, or in the event that the quorum of the Bureau is not attained for whatever reason, the Subcommittee shall entrust a member to act in that capacity as required, temporarily, in accordance with the process provided for in paragraphs 2 and 3 of the present rule. V. Other positions Rule 21 Rapporteur on reprisals and other positions 1. The Subcommittee shall appoint a member, for a period of two years, if possible by consensus, to act as its rapporteur on reprisals. 8