The House of Lords held that the only thing that mattered was whether a reasonable person could have relied on the conduct that looked like an assurance.
Lord Hoffmann said that speaking in oblique and allusive terms does not matter if one could reasonably believe one was being given an assurance.
He said though he would not disagree about proprietary estoppel, he would ‘find it easier and more comfortable to regard David’s equity as established via a remedial constructive trust.’ The elements of a claim are clear assurance, reasonable reliance, substantial detriment.
The court should not search for ambiguity or uncertainty, but should assess the question of clarity and certainty practically and sensibly, as well as contextually.
Again, this point is underlined by the authorities, namely those cases I have referred to in para 78 above, which support the proposition that, at least normally, it is sufficient for the person invoking the estoppel to establish that he reasonably understood the statement or action to be an assurance on which he could rely.
Thirdly, as pointed out in argument by my noble and learned friend Lord Rodger of Earlsferry, there may be cases where the statement relied on to found an estoppel could amount to an assurance which could reasonably be understood as having more than one possible meaning.
It was also argued for the respondents that, if there was an estoppel as the Deputy Judge had decided, difficulties could have arisen if Peter had changed his mind before he died.
I should add that, if Peter had changed his mind before he died, the question as to what, if any, relief should have been accorded to David would have been a matter for the court, to be assessed by reference to all the facts.
It seems to me that it would be arguable that, even assuming that the "implicit statement" was not irrevocable, if, say in 2004, Peter had changed his mind, David would nonetheless have been entitled to equitable relief, in the light of his fourteen or more years of unpaid work on the farm.
Based on the reasoning of my noble and learned friend, Lord Scott of Foscote in Cobbe v Yeoman's Row Management Ltd [2008] UKHL 55, [2008] 1 WLR 1752, paras 18-20 and 28, the respondents contend that the identity of the property the subject of the assurance or statement relied on to found a proprietary estoppel must be "certain".
Although they reached an oral "agreement in principle", the parties had decided not to enter into a contract, but Mr Cobbe went ahead on the basis, as appreciated by Yeoman's Row, that he expected them to do so once planning permission was obtained.
In the context of a case such as Cobbe [2008] 1 WLR 1752, it is readily understandable why Lord Scott considered the question of certainty was so significant.
It is well encapsulated by Lord Walker's distinction between "intangible legal rights" and "the tangible property which he or she expects to get", in Cobbe [2008] 1 WLR 1752, para 68.
The relationship between the parties in that case was entirely arm's length and commercial, and the person raising the estoppel was a highly experienced businessman.
What Mr Cobbe then relied on was "an unformulated estoppel ... asserted in order to protect [his] interest under an oral agreement for the purchase of land that lacked both the requisite statutory formalities … and was, in a contractual sense, incomplete" - [2008] 1 WLR 1752, para 18.
On the Deputy Judge's findings, it was a relatively straightforward case: Peter made what were, in the circumstances, clear and unambiguous assurances that he would leave his farm to David, and David reasonably relied on, and reasonably acted to his detriment on the basis of, those assurances, over a long period.
Concentrating on the perceived morality of the parties' behaviour can lead to an unacceptable degree of uncertainty of outcome, and hence I welcome the decision in Cobbe [2008] 1 WLR 1752.
However, it is equally true that focussing on technicalities can lead to a degree of strictness inconsistent with the fundamental aims of equity.
The notion that much of the reasoning in Cobbe [2008] 1 WLR 1752 was directed to the unusual facts of that case is supported by the discussion at para 29 relating to section 2 of the Law of Property (Miscellaneous Provisions) Act 1989.
Section 2 may have presented Mr Cobbe with a problem, as he was seeking to invoke an estoppel to protect a right which was, in a sense, contractual in nature (see the passage quoted at the end of para 96 above), and section 2 lays down formalities which are required for a valid "agreement" relating to land.