But the relevant statute *doesn't* recognise any such category. That is the point. In a statute which sets out to be comprehensive and to include all possible private law claims, Parliament did not find it necessary to mention restitution or unjust enrichment.

are classified as actions "founded on a simple contract" for the purposes of s5 of the Limitation Act. This is surely unsurprising. If they were not so classified the courts would have been forced to conclude that no time limit applied to such claims as there is no specific provision within the Act dealing with them.

There is a specific category of contractual claims in the statute, which includes contracts arising by operation of law. I appreciate that you have difficulties with the notion of a contract arising by operation of law, and would like to separate 'contract' from 'restitution', but this is not a universal view, and I was discussing what the law actually is. The Act treats both varieties of contract together.

It is also true that the time period applicable is generally the same: 6 years. It is not true, however, that time starts to run from the same point.

Time runs from the accrual of the obligation. In the example we were discussing, the obligation accrues at the same instant whether you look at the matter in 'breach of contract' terms or 'unjust enrichment terms'.

Time for claims based upon a breach of contract will generally start from breach. Time for claims based upon unjustified enrichment will generally, but not always, run from the time of enrichment.

This begs an important question, by smuggling in the assumption that there is a coherent 'law of limitation for unjust enrichment claims'. Every article I have read on the subject concludes, correctly in my view, that there is no such coherent law, and that the law is a hotch-potch, reflecting the miscellaneous nature of the claims covered. Of course, many of those articles then go on to argue that the law should be changed, to reflect some underlying order the authors think they see. This is a different issue.

Claims based upon the commission of a tort also generally carry a time limit of six years. Where a claim for breach of contract and the commission of a tort exist concurrently the different points at which time may begin to run can provide an incentive for the pleading of the claim in tort rather than in contract (Henderson v Merrett). The same may be true where a claim based upon unjustified enrichment exists concurrently with a claim for breach of contract.

That would be so if the contract/restitution line could be drawn in the same way as the contract/tort line. But for a number of reasons, which will be apparent on reading any good text on the history of private law, the lines are of a very different character, and the separation of contract from restitution incomplete at best.

Steve Hedley