15.7.—(1) A party may put written questions to—
(a)an expert instructed by another party; or
(b)a single joint expert appointed under rule 15.12,
about a report prepared by such a person.
(2) Written questions under paragraph (1)—
(a)may be put once only;
(b)must be put within 28 days beginning with the date on which the expert's report was served;
(c)must be for the purpose only of clarification of the report; and
(d)must be copied and sent to the other parties at the same time as they are sent to the expert.
(3) Paragraph (2) does not apply in any case where—
(a)the court permits it to be done on a further occasion;
(b)the other party or parties agree; or
(c)any practice direction provides otherwise.
(4) An expert's answers to questions put in accordance with paragraph (1) shall be treated as part of the expert's report.
(5) Paragraph (6) applies where—
(a)a party has put a written question to an expert instructed by another party in accordance with this rule; and
(b)the expert does not answer that question.
(6) The court may make one or both of the following orders in relation to the party who instructed the expert—
(a)that the party may not rely upon the evidence of that expert; or
(b)that the party may not recover the fees and expenses of that expert, or part of them, from any other party.
(7) Unless the court directs otherwise, and subject to any final costs order that may be made, the instructing party is responsible for the payment of the expert's fees and expenses, including the expert's costs of answering questions put by any other party.