contract law concerns enforceable promises, and can be summed up in the latin phrase "pacta sunt servanda" (agreements must be kept). in common law jurisdictions, three key elements to the creation of a contract are necessary: offer and acceptance, consideration and the intention to create legal relations. in "carlill v carbolic smoke ball company" a medical firm advertised that its new wonder drug, the smokeball, would cure people's flu, and if it did not, the buyers would get £100. many people sued for their £100 when the drug did not work. fearing bankruptcy, carbolic argued the advert was not to be taken as a serious, legally binding offer. it was an invitation to treat, mere puffery, a gimmick. but the court of appeal held that to a reasonable man carbolic had made a serious offer, accentuated by their reassuring statement, "£1000 is deposited". equally, people had given good consideration for the offer by going to the "distinct inconvenience" of using a faulty product. "read the advertisement how you will, and twist it about as you will", said lord justice lindley, "here is a distinct promise expressed in language which is perfectly unmistakable".