Slater Wilmhurst Ltd v Crown Group Custodian Ltd [1991] 1 NZLR 344 is a cited case in New Zealand regarding common mistake.

[1][2][3] In 1980, Slater Wilmhurst, a property developer, built a retail building in Lower Hutt, and arranged the retailer Hallenstein Bros to lease the building, with the lease agreement giving them first right of purchase.

One month later, Slater Wilmhurst accepted an offer from Cromwell Corporation to sell the building for $2.587 million.

However, this time, Cromwell's solicitors did a title search, which brought to their attention of Hallensteins right to purchase, and upon contacting Hallensteins to confirm whether they wanted to exercise their option, the elected to purchase the building.

The court ruled in favour of Slater Wilmhurst and awarded damages of $345,000.