Foedera, conventiones, literae, et cuiuscunque generis acta publica inter reges Angliae et alios, ed. Thomas Rymer (20 volumes, 1727-1735). [A collection of many diplomatic documents transcribed in their original language]
Rymer's Foedera: Syllabus in English with Index, 1066-1654, ed. D. Hardy (3 volumes, 1869-1885)
We know from Rymer’s Foedera that the reign of Henry II produced several diplomatic treaties, of which only one remains. The surviving document details the number of knights Flanders needed to supply to the King. Other documents include Henry accepting the homage and fealty of the Kings of Ireland and Scotland, as well as him making peace with the King of France and his own sons after the Great Revolt. Treaties from Richard reign frequently involve his crusading exploits, especially temporary cessations of violence with France to support that end. From John’s reign comes the most known treaties, notably those dealing with his disputes with the pope and the insurrection of his barons. Marriage contracts are frequent, as marriage itself was a form of diplomatic peacekeeping.
While the treaties themselves differed in form and style, they are indicative the new way that treaties were formed during Henry II’s reign. The treaties were made out in both rulers names, with both rulers typically being present during their creation. These meetings took place in “middle ground” between the lands of both rulers. In the case of Henry’s treaties with the Kings of France, they took place in the marches of Normandy. They were created in duplicate so both parties would have one. During Richard’s reign we see England adopt a more standardized format for the treaties, which had been popularized in France. Especially important was the use of proctors, who were authorized to deal on the ruler’s behalf, with the understanding the ruler would be held by oath to deals made in his name. Under John we see the most significant attempt to standardize and keep record of diplomatic documents. The royal chancery transcribed documents issued under the royal seal on yearly rolls.
Chaplais, Pierre. 2003. English Diplomatic Practice in the Middle Ages. London ; New York : Hambledon and London, 2003.