Lambert Simnel said:
There is also circumstantial evidence that there was a Jewish dynasty in Provence during the early dark ages. If I recall correctly all that is known about them is that they had a succession of rulers with old testament names, from which it has been theorized that they were Jewish
You're referring to Septimania...
In Eighth century France, Jews established a glory that is not only embedded in grandiose and gracious living but also reputed itself in greatness of Torah studies and a learning capacity that enjoyed recognition second to none. While all this seems too good to be true in reality the story is not quite as perfect as it seems. All this goodness was bestowed on the Jews by Pepin the Short on a small Jewish community in Southern France, on the border of Spain, at the fortress city of Narbonne in the territory of Septimania in return for help given by the Jews to Pepin in driving out the Islamic Moors from the city.
Under Pepin the Short it was a politically prudent thing to confirm Septimanian independence under the rulership of a Nasi (Potentate) of Judah. The decision was also upheld by the Caliph of Baghdad and reluctantly, by Pope Stephen the III in Rome. How did all this come about?
A document (also known as a Gesta) gives credit to the Jews for the fall of Narbonne to the Franks. As a reward a delegation of Narbonne Jews requested permanent kingship of their own and at the same time offering a handsome gift of 70,000 mark silver to Charlemagne the son of the Great Pepin the Short. Charlemagne agreed to the gift and terms. Witness to the negotiations were the Pope Stephen III , 768 CE and many barons. When the town fell Charlemagne kept his promise. He gave the Jews their Principate or Princedom and ceded to them one third of Narbonne.
While the Jews were permitted to own land and even have Christian slaves run their homes and farms, a great Academy rose in Narbonne which attracted the greatest of scholars from Palestine as well as Babylon. At the time this was chronicled in 705 CE there were but a mere 300 Jews in the area. The author of that statement is one Abraham ibn Daud author of Sefer Seder HaKabbalah (The book of the Order of the Kabalah also known as the SKh) which was completed in 1160-61. (Figuring that there were approximately six people to an average household, we are talking about 1800 to 2000 people).
http://www.jewishmag.com/105mag/jewishacademy/jewishacademy.htm
The area of Septimania started showing up in popular culture after the publication of the 1982 pseudohistorical book Holy Blood Holy Grail and the later fame around the related 2003 bestselling novel, The Da Vinci Code. This resulted in Septimania being mentioned on television "debunking" documentaries such as the 2006 Da Vinci Declassified on The Learning Channel.
In Holy Blood Holy Grail, the claim was made that as part of the territory disputes around Septimania in the 8th century, a small Jewish kingdom was established by Charles Martel's son Pippin the Younger, as a way of tipping the power balance in the embattled city of Narbonne. According to the book, a pact was made to this effect in 759, and when the Jewish population rose up in 768 and evicted the Muslim controllers, Pippin kept his part of the bargain and established an official Jewish principality. It was to owe allegiance to Pippin (called "Pepin" in the book), but otherwise maintain independence. The installed ruler was allegedly a man named Aymery, who, when received into the ranks of Frankish nobility, took the name Theodoric, or Thierry. The man's origin was uncertain, with the book claiming that he was possibly of Merovingian descent, or may have been a native of Baghdad who was descended from Babylonian Jews during the Babylonian captivity. The Merovingian claim was important to the book, since the actual Merovingian dynasty had been destroyed in 679, when King Dagobert II had been assassinated, though the book claimed that his son had been rescued and transported to the home of his mother, in the Septimania region, in the village that is now known as Rennes-le-Chateau.
The book further stated that Theodoric was recognized by both Pepin and the caliph of Baghdad as "the seed of the royal house of David", and married a woman named Alda, who was an aunt to Charlemagne. The region was endowed with estates "held in freehold from the Carolingian monarchs" and was granted tracts of Church land as well, against the wishes of Pope Stephen III. Theodoric ruled the principality, and this crown was later given to his son, William of Gellone, whose bloodline later produced the Dukes of Aquitaine.
The reason for the book's claims, was an attempt to prove a blood link between the House of David and Frankish royalty, specifically the Merovingians, as a way of showing that the Merovingians were the descendants of a bloodline starting with the child of Jesus and Mary Magdalene.
http://en.wikipedia.org/wiki/Septimania