"Bullock v London General OmnibusCo [1907] 1 KB 264"

Rule 14-1(18): If the costs of one defendant against a plaintiff ought to be paid by another defendant, the court may order payment to be made by one defendant to the other directly, or may order the plaintiff to pay the costs of the successful defendant and allow the plaintiff to include those costs as a disbursement in the costs payable to the plaintiff by the unsuccessful defendant.

Why do you think this case initiated the order for payment of costs?