Complex sentence: At a brief trial, Gaveston was declared guilty of being a traitor under the terms of the Ordinances; he was executed on Blacklow Hill the following day, under the authority of the Earl of Lancaster.
Split into simpler sentences: At a brief trial Gaveston was declared guilty of being a traitor under the terms of the Ordinances. He was executed on Blacklow Hill the following day under the authority of the Earl of Lancaster.