Dragonborn

The dragonborn come to England as a result of the Norman Invasion of 1066 as William's allies and mercenaries. William the Bastard was Duke of Normandy and one of the claimants to the English Throne, promised the crown by Edward the Confessor. His distant cousin, Harald Hardraga also was a claimant and both invaded. Harald was defeated but William defeated Harold Godwinson by simple blind luck. As a result of his victory, William gave his dragonborn allies the right to settle in Salisbury, Wiltshire, and Hampshire. As a result, they displaced the Jutish Anglo-Saxons there. The dragonborn speak draconic first, Norman French second, and English last.

From Arc Teryx
All dragonborn in England are from Arc Teryx, an island kingdom of dragonborn composed of the islands of Corsica and Sardinia. The Arc Teryx dragonborn are allied with France. With the invasion of England complete, the dragonborn sent for their families and become part of the new Nobility.

Population Centers
The Dragonborn are strongest in population in old Sarum. But are diffused throughout England as part of William's program of replacing English lords with norman ones. The current Earl of Salisbury, though, is a dragonborn -- one Lord Belcrath.