The source of the Common law rule that an action of covenant would lie only on an agreement embodied in a sealed deed is enshrouded in mystery. It was obscure for John Reeves, the author of the first substantial history of English law, who alludes to it when dealing with the reign of Edward II but not when dealing with the reign of Edward I. A century later F W Maitland was inclined to think of it as a rule dating from ‘before the end of the reign of Edward I’, though was somewhat confused by a case of 1234 which appeared to show (but did not in fact do so) that there was already then a requirement of writing. T F T Plucknett and Sir William Holdsworth seemingly followed Maitland in placing it in the reign of Edward I. For Brian Simpson in 1975, as for James Barr Ames before him, it was a rule which had always existed, though by then scholarship was beginning to settle on the reign of Edward II as the crucial period for the establishment of the rule. Toby Milsom asserted this without greater precision being made explicit, while in the first edition of his Introduction to English Legal History John Baker anchored this to the Waltham Carrier Case in the 1321 Eyre of London. This is still seen as the date by which the rule was firmly settled in the current edition of the work.