Eustace the Monk - Reconquest of Channel Isles
Jersey 1204 is not clear as to how the Channel Isles fared politically in 1204, Peter de Peaux held the isles in fief to King John prior to surrender to the French at Rouen, whereby he transfered his holdings to French sovereignty. Jersey 1204 postulates that he did indeed pass the islands into French hands. Whatever the process King John needed to reconquer the islands.
"An important source for the first Plantagenet campaign of reconquest is a work of literature the 'Romance of Eustace the Monk'. ... the 'Romance' as a source of political history is problematical but some of the material in the 'Romance' can be corroborated and dated from other sources"
Eustace was thought "ambitious and self serving, and also that he was indeed recognised as an exceptionally skilled seaman"
In 1205 King John employed Eustace on an expedition to the Channel Isles equipped with 30 galleys, which may have been a successful raiding/pirate sortie but it seems did not capture the islands. In 1206 John tried again with five galleys and three great ships, but possibly not Eustace, because it is Geoffrey de Lucy and Hasculf de Subligny who are ordered to return the ships the reconquest having been successful.
At some point Eustace establishes himself on Sark "this probably originated with a grant from King John, .. ,but Eustace finally lost the Kings favour. In 1214, Plantagenet forces raided Sark and took possession of the island for the Crown. In the raid, Eustace's brother and uncle, their servants and men at arms were captured and taken as prisoners to Porchester Castle, but Eustace remained at liberty."
It would appear that after 1214 Eustace operated on behalf of the French King, Philip Augustus, and took virtual control of the Channel "Eustace the Monk and his associates 'who keep the sea ways'"
Despite releasing hostages held against the Islands' good behaviour it seems that John and his successor Henry III had again lost control of the Islands by 1217. The islands were recovered for a second time by the Treaty of Lambeth when the loss of Eustace after the Battle of Dover lost France control of the Channel and with it any chance of resupplying Prince Louis's campaign in England.