As has earlier been stated, consideration need only be sufficient not adequate. It must have value in the eye of the law. The scope of what is valuable in the eye of the law has no judicial analysis however, legal scholars have contributed much to the subject. According to Cheshire and Fitfoot, the judges have been content to deny the name of consideration to certain acts or promises without attempting to generalize the grounds of their prohibition and it may well be that the process of judicial thought is empirical and may not lend itself to ex post facto rationalization.
Consideration must not be of monetary or economic value to be sufficient in the eye of the law. According to JC Smith, all that is necessary is that the defendant should, expressly or impliedly ask for something in return for his promise or act. If he gets what he asked for, then the promise is sufficient consideration unless there is some vitiating factor. Thus, consideration does not have to be of economic value, it must be clear that it was what the defendant requested, it may be quite useless to either party and it must be something owned by the party giving it out or at least something he is entitled. See
Bainbridge v. Firestone (1838) 8 A&E 743 and Haigh v. Brooks (1839) 10 A&E 309.
There are cases where performance of a duty is not sufficient consideration. They are;
1. Performance of a duty imposed by law: A party cannot enforce a promise made to him in exchange for his legal duty. Since he’s under a public duty, his actual performance or promise to do so does not constitute consideration. See Collins v. Godefroy (1831) 1 B & Ad 950. If, however, the plaintiff acts or promises to act in excess of his duty under the law, then this would constitute consideration. See Glassbrook Brothers LTD v. Glamorgan County Council (1925) AC 270.
2. Performance of a duty imposed by contract with a promisor i.e where plaintiff is already under contractual duty to defendant. If a party to a contract simply promises to carry or carries out an already existing contractual duty to the defendant, he has offered no consideration for any fresh promise that might have been made by the defendant. See Stilk v. Myrick (1809) 2 Camp. 317.
However, as is the case with duties imposed by law, if the plaintiff act or promises to act in excess of his contractual obligation to the defendant, such a promise would constitute consideration. See Hartley v. Ponsonboy (1857) 7 E&B 872.
3. Performance imposed by contract with a third party: this is the situation in which X, who is already bound by contract to do something for Y, relies on the performance of that act as consideration for a fresh promise made to him by Z. Unlike the two earlier situations, the courts have consistently held that in relation to the new promise made by Z, X’s performance of his already existing obligation to Y is good consideration. See Scotson v. Pegg (1861) 6 H&N 295.
https://lawstudentaide.com/2019/01/21/sufficiency-of-consideration/