1Where parties agree that mesne profits are to be measured by market rent, market rent is an objective measure to be established by evidence; where the only evidence of rental value is a composite agreement comprising a lease and an incentive deed, both documents must be taken into account in determining market rent, and the face rent under the lease alone does not necessarily represent market rent
2A trial judge errs in the exercise of the costs discretion by taking into account, in favour of a successful plaintiff who abandoned a claim, that the defendant is likely to benefit from that abandonment through res judicata or Anshun estoppel — such a consideration is irrelevant to the proper exercise of the costs discretion
3Where a clearly separable issue has been abandoned by the successful party, an issue-by-issue approach to costs may produce a fairer result than a broad percentage reduction, and the matter may be referred to the taxing officer to determine the appropriate allocation
