Where the court gives a direction under rule 15.12 for a single joint expert to be used, the instructions are to be contained in a jointly agreed letter unless the court directs otherwise.

Where the instructions are to be contained in a jointly agreed letter, in default of agreement the instructions may be determined by the court on the written request of any instructing party copied to the other instructing parties.

Where the court permits the instructing parties to give separate instructions to a single joint expert, unless the court directs otherwise, when an instructing party gives instructions to the expert, that party must at the same time send a copy of the instructions to the other instructing party or parties.

The court may, before an expert is instructed, limit the amount that can be paid by way of fees and expense to the expert.

Unless the court directs otherwise, and subject to any final costs order that may be made, the instructing parties are jointly and severally liable for the payment of the expert's fees and expenses.