War With France? Not Likely.

While I think that this is very unlikely, there are some interesting historical points about the island where the recent fishing dispute has occurred. For those who may not be familiar with the issue, some French fishermen have threatened to blockade a port on the British island of Jersey, and both countries have sent Navel vessels to the area. The island of Jersey is one of the Channel Islands which are a Crown Dependency of the United Kingdom.  While Jersey and the Channel Islands are Crown Dependencies of the United Kingdom, they are not actually part of the United Kingdom.  Now why are these islands right off the coast of France British Crown Dependencies you ask.  Well let me tell you.   Jersey, Guernsey and a few other islands are part of the region of Normandy.  Now I am not referring to a region in the political sense, as the majority of Normandy is part of France, but of a geographical region.  This dates back to the Duchy of Normandy.  I may have to go back in time a bit.
 If we go back to AD 911 to a Viking named Rollo, yes, he was played by Clive Standen in History Channel’s Vikings.  He was not however the brother of the semi-legendary Viking King Ragnar Lothbrok, but that is a story for another day.  In short Rollo became the first Duke of Normandy when the King of West Francia, Charles the Simple gave him the lands in exchange for his loyalty and protection from other Vikings, as well as an agreement to stop attacking his lands.
Now nothing overly significant (to our story) happens until Rollo’s descendant William the Conqueror invades and conquers England in 1066.  Now on top of being Duke of Normandy (as a vassal of the King of France) he was also King of England in his own right.  This sounds like a complicated situation.   
By the time of King Henry II of England (1154-1189) the House of Plantagenet had become the ruling house of England and also ruled more then half of France by way of various duchies and counties as vassals of the King of France.  Now of course the English King held much more power than the French King and the vassalage was more of a formality.  Now if anyone knows anything about British-French relations, this seems like a high point.  Unfortunately, Henry II had to fight multiple wars against his sons, because that family really did not get along. 
Eventually Henry II died, and his son Richard the Lionheart became King.  While he was off fighting in the Holy Land, his brother Prince John rebelled against him. This is the historical backdrop that Robin Hood was set against.  Richard would eventually be killed in battle in France and his brother John would become King in 1199 but would lose most of his French territories in 1214 and would then be forced to sign the Magna Carta the next year. He is not remembered very fondly.
While Normandy had been lost to the French Crown, the Channel Islands remained in English hands.  They were however, never made part of the Kingdom of England and remain Crown Dependencies to this day.
John was not the English King who lost all of the English held lands in France.  The story between England and France gets more interesting.  In 1308, Princess Isabella, daughter of King Philip IV of France was married to King Edward II of England and gave birth to their first son, the future King Edward III in 1312.  Now Mel Gibson would have us believe that he was in fact the bastard son of William Wallace who died in 1305, seven years before his birth.  What is also concerning, is that Isabella would have only been three years old during the conception.
She was married to Edward II for the purpose of an alliance. What France did not count on was that Philip IV and all three of his surviving sons (Louis X, Philip V, and Charles IV) would all die by 1328 without heirs, meaning that King Edward III of England (the grandson of King Philip IV) now had an incredibly significant claim to the French throne.  The English and later British monarchs would claim the title King and Queens of France for the next 500 years.
This led to the Hundred Years War.  Edward III himself, was not able to sit on the throne of France.  He had many sons, who had sons who did not get along with each other, we will get to that.  King Henry V of England was able to invade France and force the French King to capitulate and name him as his heir, and the daughter of the French King was once again married off to the King of England. 
Henry V would die young and the French King soon after him, resulting in his son Henry VI being crowned King of both countries.  Henry VI would end up losing all his lands in France and would later be disposed not once, but twice from the English throne (1461, 1471) in the Wars of the Roses which was fought between the Houses of Stark and Lannister, I mean York and Lancaster.
The claim to the French throne would last longer than the French monarchy when it was finally dropped in 1802.  This led to an interesting situation for the Channel Islands as England and later Britain had considered them to be part of France.  This was when they formally became Crown Dependencies.
So, there you go, an 1100-year explanation of why there are British Islands right off the coast of France, who aren’t actually part of the United Kingdom.