Thomas de Seton

[His father, Alexander] was governor of the town of Berwick when it was besieged by the English in 1333. His son [this person,] Thomas was given as a hostage to King Edward III., that that place would be surrendered on a certain day if not relieved before then. Sir William Keith, having arrived with succours, assumed the governorship, and refused to deliver up the town. Edward ordered Thomas Seton, and, some accounts say, two sons of Keith who had fallen into his hands, to be executed in sight of the besieged.

Source: Electricscotland.com - Google (17.6.2010)