An offer must be made by a person legally competent to contract or on his behalf, by someone authorised by him to make the offer. It is usually made to a person (or to a number of persons), but it can be made to the entire world, as happened in Carlill v. Carbolic-Smoke Ball. Co., [(1893) 1 QB 256: (1881-94) All ER 127]. In that case, the defendants (manufacturers of medicinal smoke balls) promised to pay £100 to anyone who, after having bought and used their smoke balls, caught influenza. Plaintiff did so and caught influenza. Plaintiff was held entitled to recover. It was no defence that there was no particular individual to whom the announcement was addressed. Such contracts are sometimes called “unilateral contracts” – not a very happy term, because a contract can never be “unilateral”. There must be two parties. It is really a case of innumerable offers, made to all potential readers of the announcement.