11.2.7 to extend before or after their expiry, or abbreviate any time limits provided for in these Rules or by his rulings or directions;

11.2.8 to appoint one or more advisors or experts on any matter (including law) to assist in the conduct of the arbitration, but only with the agreement of all parties and of such advisor or experts, and only if the parties and such advisors or experts have agreed on the payment of the fees of such advisors or experts directly by one or more of the parties;

11.2.9 to order any party who is a claimant, or claimant under a counterclaim, to furnish security for costs in respect of his claim or counterclaim;

11.2.10 to allow (but only with their express written consent) other parties to be joined in the arbitration proceedings, and to make an award on all issues submitted by all parties,

including parties so joined, for decision by the arbitrator;

11.2.11 to determine the existence or validity of any contract, including any contract containing the arbitration agreement, and to order rectification of such contract;