(ii) Waiver of the Cause of Action
The doctrine of waiver of tort can be interpreted in another way, as recognized by Peter Gibson LJ in Halifax Building Society v Thomas,11 who defined the doctrine ‘as meaning that the [claimant] chooses not to sue in tort for damages but sues instead in restitution for the recovery of the benefit taken by the wrongdoer’. Although the phrase ‘sues instead in restitution’ is ambiguous, what the judge appears to have meant was that the claimant could waive a cause of action in tort in favour of a cause of action ‘in restitution’. In other words, where the claimant is the victim of a tort then, rather than found the restitutionary claim on the defendant’s wrongdoing, he or she may be able to bring a cause of action which is founded on the reversal of unjust enrichment. This sense of waiver of tort therefore involves alternative analysis.[1] So, for example, if the defendant induced the claimant to pay money to him or her by virtue of a fraudulent misrepresentation, the claimant might sue the defendant for the tort of deceit or might instead bring a claim founded on the defendant’s unjust enrichment, with the ground of restitution being induced mistake. Similarly, if the defendant has falsely imprisoned the claimant and made it a condition of release that the claimant should pay a sum of money to the defendant, the claimant can base a restitutionary claim either on the tort of false imprisonment or, by a claim founded on the unjust enrichment principle, with the ground of restitution being duress of the person.[2]
Although the claimant’s election to bring a claim grounded on the unjust enrichment principle rather than tort makes it appear that he or she has waived the tort, this is only true in a purely descriptive sense. It is not technically true because simply by basing the claim on unjust enrichment does not extinguish the tort. As was recognized by the House of Lords in United Australia Ltd v Barclays Bank Ltd,14 the claim in tort will only be extinguished once final judgment has been obtained against the defendant. Until that point the claimant is able to discontinue the proceedings based on unjust enrichment and commence proceedings founded on the tort. Where the claimant founds the claim in restitution on the defendant’s unjust enrichment the claimant is not waiving the tort but is simply ignoring it.15
