"(a) It is a commonplace that a successful party will not succeed on every aspect of its case. But notwithstanding that very frequent occurrence in litigation, the general rule still applies. Costs are determined by reference to overall success ..... (c) A degree of caution is needed against a too-ready departure from the general rule for the reasons explained by Jackson LJ in Fox v Foundation Piling ..... (d) There is no reason in principle why a party who succeeds in establishing one element of his cause of action but fails to establish the others should be regarded as partially successful ..... (g) It is, of course, not the law that a successful party can only be deprived of the costs of an issue if has unreasonably resisted that issue: any more than it is the law that he should be deprived of the costs of the issue simply because he lost it. In singling out an issue for separate treatment by way of costs I think the court must look for some objective ground (other than failure itself) which alongside failure distinguishes it from other issues and causes the general rule to be disapplied ... Without seeking in any way to be prescriptive, I think the distinctive ground may relate (amongst other things) to the comparative weakness of an argument (even if not unreasonably maintained) or to the necessity for particular evidence relevant only to that issue or to extensive and intensive legal argument directed to that issue which gives it an especial significance in the costs context."