The claimant lost against the defendant, and so the Third Party joined to the proceedings by the defendant did not have to indemnify the defendant. There was no dispute that the claimant should pay the defendant's costs. Of issue here, though, was who should pay the Third Party's costs.
Nicol J noted that, under the general rule that additional claims are treated as if they are claims, and the loser pays the winner's costs, that would result in the defendant having to pay the Third Party's costs. However, that is only the starting point. According to the White Book, where the claimant is not impecunious (and that was not the case here, the claimant having adequate insurance cover), the claimant should usually be liable for the costs of both the defendant and the Third Party.
In this case, though, there had been an additional reason as to why the Third Party would never have been liable even if the claimant had won, and so it had not been reasonable for the defendant to join it to the proceedings. Accordingly, it was concluded that the claimant should not pay all the Third Party's costs. Nor was it relevant that the claimant had sufficient insurance cover: "insurance is a precaution against liability, not the cause of liability".
However, the claimant had chosen to obtain disclosure by encouraging the Third Party proceedings to continue, and so the claimant was ordered to pay the Third Party's costs up to the end of disclosure (and the defendant had to pay the Third Party's costs thereafter).