The point appears most clearly in the judgment of Goff LJ: Daulia Ltd v Four Millbank Nominees Ltd [1978] 2 WLR 623, CA, p 624

Daulia Ltd v Four Millbank Nominees Ltd [1978] 2 WLR 623, CA, p 624 Goff LJ: I therefore turn to the first question. Was there a concluded unilateral contract by the first defendants to enter into a contract for sale on the agreed terms? The concept of a unilateral or ‘if contract’ is somewhat anomalous, because it is clear that, at all events until the offeree starts to perform the condition, there is no contract at all, but merely an offer which the offeror is free to revoke.