"... where litigation had been settled save as to costs there was no convention that there should be no order as to costs ... the court's overriding object was to do justice between the parties without incurring unnecessary court time and additional cost; that where it was obvious which party would have won had the substantive issues been fought to a conclusion it would be appropriate to award costs to that party; that where that was not obvious, the extent to which the court would be prepared to look into the previously unresolved substantive issues in order to determine the issue of costs would depend on the circumstances of the case, including the amount of costs at stake and the conduct of the parties; that in the absence of a good reason to make a specific order the court would make no order as to costs ..."