The juridical basis for interest on money repaid following variation of a judgment on appeal is unjust enrichment, not damages. The purpose is to restore to the successful appellant what was taken, not to compensate for loss. The court may use its own experience and memory of prevailing rates to fix an appropriate interest rate rather than requiring evidence of the payee's actual return on the money. Where an appellant succeeds on only one ground, a proportionate costs order (here 30%) may be appropriate.
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