Lincoln Castle was again besieged before the Second Battle of Lincoln, on 20 May 1217, during the reign of Henry III of England during the course of the First Barons' War. This was the period of political struggle that followed the sealing of Magna Carta on 15 June 1215. After this, a new barbican was built onto the west and east gates. In 1375, one Agatha Lovel—"notoriously suspect" in the murder of her master, Sir William de Cantilupe—escaped justice by bribing her Lincoln Castle gaolers, where she had been imprisoned awaiting trial. The bailiffs, Thomas Thornhaugh and John Bate, were later arrested and tried for allowing Agatha to escape justice, but were either pardoned or acquitted.