What is the effect of R. 57 of the double costs rule on an offer to settle?

The words of Meredith J. are apt as they appear in Upton v. Walker (1977), 1977 CanLII 334 (BC SC), 3 B.C.L.R. 4 at 5 - 6 (S.C.): ''Before the enactment of R. 57, a plaintiff wishing to avoid the heavy costs of litigation (for which there was only marginal recovery even were the plaintiff successful) might make an offer to settle. In doing so he would risk sacrificing a larger figure that the court might award after trial but the costs of the litigation would be avoided. The double costs rule gives the plaintiff additional incentive to attempt a pre-trial settlement and an additional inducement to a defendant to treat pre-trial offers seriously. It seems to me, in fairness, that should the judgment of the plaintiff in making a pre-trial offer be vindicated, double costs should ordinarily follow the event. Unless this were the result the effectiveness of the rule would be eroded. I think I should be guided by these considerations in the present case,…. "It is also argued that the amount of the recovery by the plaintiffs is only slightly in excess of the offer, and thus that the action was not wantonly or imprudently defended. Be that as it may, the offer was refused deliberately and with knowledge of the risk. The costs of the trial have been incurred. It seems to me that to accede to that argument would be to erode the effectiveness of what must be regarded as a salutary rule."