Blimey, who declared this Estoppel month? The latest is Powell & Anor v Benney  EWCA Civ 1283. Although the case itself is not that interesting, the judgment is worth a look as it gives a clear overview of the Court of Appeal’s current thinking in this area. The only judgment is by Sir Peter Gibson.
The distinction between a ‘bargain’ form of estoppel in which relief should vindicate the Claimant’s expectations and a ‘non-bargain’ form in which relief is open to a wider judicial discretion including proportionality with detriment, as proposed by Robert Walker LJ in Jennings v Rice, is followed in this case. However, interest is expressed in a critique of this distinction by Simon Gardner in ‘The remedial discretion in proprietary estoppel – again” in (2006) 122 LQR 492.
The bargain form is potentially close to constructive trust in that an effectively contractual arrangement has been reached which would be effective save for s 2 of the Law of Property (Miscellaneous Provisions) Act 1989, such that fulfilling the expectation is akin to establishing the beneficial ownership. Akin, but not the same. The Court adopts Lord Justice Walker’s comment in Stack v Dowden that:
I have to say that I am now rather less enthusiastic about the notion that proprietary estoppel and ‘common [intention]’ constructive trusts can or should be completely assimilated. Proprietary estoppel typically consists of asserting an equitable claim against the conscience of the ‘true’ owner. The claim is a ‘mere equity’. It is to be satisfied by the minimum award necessary to do justice (Crabb v Arun District Council  Ch 179, 198), which may sometimes lead to no more than a monetary award. A ‘common intention’ constructive trust, by contrast, is identifying the true beneficial owner or owners, and the size of their beneficial interests.
The Court is firm that where the claim is against the conscience of the ‘true’ owner, it is satisfied by the minimum award necessary to do justice. Where the elements of a common intention constructive trust are not made out, it cannot simply be used or pleaded interchangeably with proprietary estoppel, as apparently happened in this case.
Gardner argues that a wider judicial discretion should be available in all proprietary estoppel cases. On the case as pleaded here, the Court couldn’t pursue this further, but I think the indication that this is the direction in which it is leaning is clear, particularly in the distinction drawn against constructive trust.
What is more clearly indicated is that a detrimental reliance on a promise must be clearly established. Any benefit also obtained can and should be considered against the detriment (at least in a non-bargain case). The scale of the detriment is key and must be carefully pleaded.
Anyone looking to claim proprietary estoppel should be thinking very carefully about both pleadings and evidence, I’d say.