What is the equitable contribution of an insurer to a plaintiff's insurance policy when they are injured in a motor vehicle accident?

It is a well-established principle of insurance law that where an insured holds more than one policy of insurance that covers the same risk, the insured may never recover more than the amount of the full loss but is entitled to select the policy under which to claim indemnity, subject to any conditions to the contrary. The selected insurer, in turn, is entitled to contribution from all other insurers who have covered the same risk. This doctrine of equitable contribution among insurers is founded on the general principle that parties under a coordinate liability to make good a loss must share that burden pro rata. It finds its historic articulation in the words of Lord Mansfield C.J. in Godin v. London Assurance Co. (1758), 1 Burr. 489, 97 E.R. 419, at p. 420: If the insured is to receive but one satisfaction, natural justice says that the several insurers shall all of them contribute pro rata, to satisfy that loss against which they have all insured.