Heralds served a very intricate and indispensable role in medieval warfare, that of being a messenger between warring sides. The performance of this role as messenger allowed them with diplomatic immunity as we would know the term today. Their person was sacred and inviolable. Capturing them was not only considered bad manners it was a violation of the Rules of Chivalry.
Jheanne complained of this to the English in a letter dated around late March or early April 1429...
"I would have sent you this letter in a more suitable manner, but you keep back my heralds: you have kept my herald Guyenne; I pray you to send him back, and I will send you some of your people who have been taken at the Fort of Saint Loup, for all were not killed there."(1) FATHER JEAN PASQUEREL. Order of Hermit Friars of Saint Augustin
Not having a herald she sent the message via an arrow.
Heralds were classed as Officers of Arms. They began their carriers as a pursuivant, then after a time became heralds, and then King of Arms. All heralds changed their surnames to their provence or had them changed as the result of enobling as a reward for their services.
These two heralds were no doubt persuivants, Dukes, Counts and Viscounts had the right to heralds, Kings of Arms were reserved for a King, Prince and Sovereign Duke, (The Duc de Bourgogne was a sovereign Duke), lesser forms for nobility did not have pursuivants.
The actual identity of Ambleville was perhaps to Julien des Essars, husband of Isabeau de Vendôme (2nd sister of Jean de Vendôme, vidame of Chartres, companion of the Maid) who was Lord of Ambleville in Vexin, member by alliance of a family of an exemplary faithfulness to Charles VII and to the Duke of Orleans. As to Guyenne, he was without doubt part of the king’s household. It was a serious insult to the King of England to have an herald named Guyenne, as this province was claimed by the King of England, as a descendant of Eleanor of Aquitaine.
Heralds were often represented as a figure holding broken chains, perhaps reflecting his role as a neutral messenger.
(2) the full text of this letter is:
"You, men of England, who have no right in this kingdom of France, the King of Heaven orders and commands you by me, Jeanne the Maid, that you quit your strong places, and return to your own country; if you do not I will cause you such an overthrow as shall be remembered for all time. I write to you for the third and last time, and shall write to you no more."
"Jhesus Maria, JEHANNE LA PUCELLE."
"I would have sent you this letter in a more suitable manner, but you keep back my heralds: you have kept my herald Guyenne; I pray you to send him back, and I will send you some of your people who have been taken at the Fort of Saint Loup, for all were not killed there."