The word "unambiguous" is explained by Kay L.J. in Low v. Bouverie [15] , the word and its explanation occurring on the same page. The Lord Justice says: "It is essential to shew that the statement was of such a nature that it would have misled any reasonable man, and that the plaintiff was in fact misled by it". Bowen L.J. says [16] : "It must be such as will be reasonably understood in a particular sense by the person to whom it is addressed". This is confirmed in George Whitechurch Ltd. v. Cavanagh [17] by Lord Brampton and in Bloomenthal v. Ford [18] by Lord Herschell.
The requirement that a representation must be clear before it can found an estoppel is, in our view, applicable to any doctrine of promissory estoppel (see Woodhouse A.C. Israel Cocoa Ltd. S.A. v. Nigerian Produce Marketing Co. Ltd.; China-Pacific S.A. v. Food Corporation of India [19] ). In the Woodhouse Case Lord Hailsham of St. Marylebone L.C. (with whose speech Lord Pearson agreed) commented [20] :
Counsel for the appellants was asked whether he knew of any case in which an ambiguous statement had ever formed the basis of a purely promissory estoppel, as contended for here, as distinct from estoppel of a more familiar type based on factual misrepresentation. He candidly replied that he did not. I do not find this surprising, since it would really be an astonishing thing if, in the case of a genuine misunderstanding as to the meaning of an offer, the offeree could obtain by means of the doctrine of promissory estoppel something that he must fail to obtain under the conventional law of contract. I share the feeling of incredulity expressed by Lord Denning M.R. in the course of his judgment in the instant case when he said [21] : "If the judge be right, it leads to this extraordinary consequence: A letter which is not sufficient to vary a contract is, nevertheless, sufficient to work an estoppel - which will have the same effect as a variation."
In the Court of Appeal [22] , Lord Denning M.R. had proceeded to refer to the higher standard of clarity required of a promissory representation relied upon to found an estoppel if compared with that required when a representation is put forward as an agreed variation of contract:
If the representation is put forward as a variation, and is fairly capable of one or other of two meanings, the judge will decide between those two meanings and say which is right. But, if it is put forward as an estoppel, the judge will not decide between the two meanings. He will reject it as an estoppel because it is not precise and unambiguous. There is good sense in this difference. When a contract is varied by correspondence, it is an agreed variation. It is the duty of the court to give effect to the agreement if it possibly can: and it does so by resolving ambiguities, no matter how difficult it may be. But, when a man is estopped, he has not agreed to anything. Quite the reverse. He is stopped from telling the truth. He should not be stopped on an ambiguity. To work an estoppel, the representation must be clear and unequivocal. That is clear from Low v. Bouverie [23] and Canadian and Dominion Sugar Co. Ltd. v. Canadian National (West Indies) Steamships Ltd. [24] .
1. [1891] 3 Ch. 82, at pp. 106, 113.
2. (1935) 52 C.L.R. 723, at p. 738.
3. [1972] A.C., at pp. 755-756, 768, 771.
4. (1924) 35 C.L.R. 355, at p. 375.
5. [1891] 3 Ch., at p. 113.
6. [1891] 3 Ch., at p. 106.
7. [1902] A.C., at p. 145.
8. [1897] A.C., at p. 166.
9. [1981] Q.B. 403, at pp. 429-430.
10. [1972] A.C., at p. 757.
11. [1971] 2 Q.B. 23, at pp. 59-60.
12. [1971] 2 Q.B., at p. 60.
13. [1891] 3 Ch. 82.
14. [1947] A.C. 46.