Jared Khan was (allegedly) born around 1208 and spent his life selling a fake elixir of life. He was contacted by Queen of the Charrl from the future on the planet Antýkhon when he was in Ercildoune, Scotland in 1270.
The Queen promised (and evidently gave) Khan eternal (or at the very least greatly extended) life and power in return for locating and taking the Doctor's TARDIS Time Vector Generator.
Khan spent seven hundred years tracking the Seventh Doctor. At various times he was an Italian count, a Jewish alchemist and a Scottish piper. (PROSE: Birthright)