Complex sentence: The charter came as a result of a petition put forward on 19 March 1513 by a guild of Deptford-based mariners--troubled by the poor conduct of unregulated pilots on the Thames--asking the king for license to regulate pilotage.
Split into simpler sentences: The charter came as a result of a petition put forward on 19 March 1513 by a guild of Deptford-based mariners. They were troubled by the poor conduct of unregulated pilots on the Thames and asked the king for license to regulate pilotage.