As these clauses are pivotal in Enclosure 5, Clauses 20.4 to 20.6 of the FIDIC Conditions (as amended) are reproduced below (in extenso):- “20.4 Obtaining Engineer’s Decision If a dispute (of any kind whatsoever) arises between the Parties in connection with, or arising out of, the Contract or the execution of the Works, including any dispute as to any certificate, determination, instruction, opinion or valuation of the Engineer, either Party may refer the dispute in writing to the Engineer for its decision, with copies to the other Party and the Engineer. Such reference shall state that it is given under this Sub-Clause. The Engineer shall decide or determine any such dispute in accordance with this Sub-Clause 20.4 [Obtaining Engineer’s Decision], acting fairly, impartially and at the cost of the Employer. In the event that the Employer replaces the Engineer, the new Engineer shall decide or determine such dispute in accordance with this Sub-Clause 20.4 [Obtaining Engineer's Decision] in place of the previous Engineer. Both Parties shall promptly make available to the Engineer all such additional information, further access to the Site, and appropriate facilities, as the Engineer may require for the purposes of making a decision on such dispute. The Engineer shall be deemed to be not acting as arbitrator(s). Within 84 days after receiving such reference, or within such other period as may be proposed by the Engineer and approved by both Parties, the Engineer shall give its decision, which shall be reasoned and shall state that it is given under this Sub-Clause. The decision shall be binding on both Parties, who shall promptly give effect to it unless and until it shall be revised in an amicable settlement or an arbitral award as described below. Unless the Contract has already been abandoned, repudiated or terminated, the Contractor shall continue to proceed with the Works in accordance with the Contract. If either Party is dissatisfied with the Engineer’s decision, then either Party may, within 28 days after receiving the decision, give notice to the other Party of its dissatisfaction. If the Engineer fails to give its decision within the period of 84 days (or as otherwise approved) after receiving such reference, then either Party may, within 28 days after this period has ended, give notice to the other Party of its dissatisfaction. In either event, this notice of dissatisfaction shall state that it is given under this Sub-Clause, and shall set out the matter in dispute and the reason(s) for dissatisfaction. Except as stated in Sub-Clause 20.7 [Failure to Comply with Dispute Adjudication Board’s Decision] and Sub-Clause 20.8 [Expiry of Dispute Adjudication Board’s Appointment], nether Party shall be entitled to commence arbitration of a dispute unless a notice of dissatisfaction has been given in accordance with this Sub-Clause. If the Engineer has given its decision as to a matter in dispute to both Parties, and no notice of dissatisfaction has been given by either Party within 28 days after it received the Engineer’s decision, then the decision shall become final and binding upon both Parties.