@sneakypete as an aside, the Knights Templar are interesting to look at wrt the beginning of banking in Europe... When the king of France (with a nod from the pope) tried to destroy them, they largely escaped and disappeared.
Shortly thereafter, the mountain highways of Switzerland began being protected by professional knights whose ensigns were unknown, but in the pattern and colors of the Knights Templar, and Switzerland began to become the banking powerhouse we've known it to be. And the Swiss banks had their fingers in the very formation of national banks, primarily in the Germanic countries...
You have to remember that banks were largely in service to feudal lords - governmental loans, primarily. where lords went to borrow were either kings or other lords, or the Roman church. The Swiss banks, largely like the Templar knights' design, were independent in all that. Swiss couriers also possessed diplomatic passage through countries just exactly like the Templars did.
Banking really didn't take off until the Protestant countries, and really not until the formation of the merchant class, hundreds of years later... which also wound up destroying the feudal system with sheer profit.
I don't think you'll find any Jewish power in banking until that time and forward - They may have been bean-counters in a position to rise, but would have no traction with the church, and little traction with kings and lords... It was the merchant class (read 'middle class') that offered a means to rise above one's station.
