What is the test for making an "all in" offer under Rule 37 of the Rules?

In my opinion, the learned judge not only erred in failing to apply the principles of Rule 37 to the issue before her, but also she failed to appreciate that Calderbank v. Calderbank, supra, does not say that an "all in" offer made outside the Rules may be considered on the issue of costs.

Calderbank v. Calderbank was a matrimonial cause. The English rules at the time made no provision for offers of settlement, save by payment in. I do not know whether the English rules have since been changed. On the 10th August, 1974, in an affidavit in an action which eventually went to trial in January 1975, the wife had deposed, "I am willing, and have always been willing, to make over to the [husband] the house at Alderley Edge." She said nothing about costs. As Cairns L.J. noted, the value of the house was about £12,000. At the trial, the learned trial judge had awarded the husband £10,000 and ordered that each party should pay his or her own costs of the proceedings.