"The court should not order an unsuccessful claimant to pay the costs of the defendant or an interested party attending an oral hearing and successfully resisting an application for permission except in exceptional circumstances. Such circumstances may exist in the presence of one or more of the following factors -- (a) the hopelessness of the claim, (b) the persistence by the claimant in the claim after having been alerted to the facts or the law demonstrating its hopelessness . . . "