Jellicoe

Maester Jellicoe is an unseen character in Game of Thrones. He was a maester of the Citadel.

Biography
Jellicoe suggested that the settlement that would become Oldtown began as a trading post where ships from Valyria, Old Ghis and the Summer Islands put in to replenish provisions and conduct repairs.

Reference

 * "Oldtown (Histories & Lore)"