Unjust enrichment, the doctrine of modern contract dates back to the 13th century English Law, known as the “Action of Assumpsit” which developed from “Trespass on the Case.” The courts at that time did not recognize our modern concept of breach of contract. According to Ranulf Glanvill, a famous legal scholar, he wrote just before the year 1200 thus, “It is not the custom of the Lord King to protect the private agreements nor does it concern itself with such contracts as can be considered private agreements.” [1] However, in the early days of English common law, the forms of actions known as Writs provided a proactive approach to the categories of civil liability and according to Maitland’s words “the forms of action we have buried, but they still rule us from their graves.” [2] This article seeks to proffer an overview of the historical development of our modern contractual terms and law.