Shortly before his 18th birthday, King Edward III, with the help of a few trusted companions led by Sir William Montagu, staged a coup d'état at Nottingham Castle (19 October 1330) against his mother Isabella of France, and her lover, Roger Mortimer, 1st Earl of March. Both Isabella and Mortimer were acting as Regents during Edward's minority following their murder of his father Edward II at Berkeley Castle. William Montagu and his companions were accompanied by William Eland, castellan and overseer of Mortimer's castle, who knew the location of a secret tunnel which would take them higher up in the castle to a normally locked door. In the dark of night on 19 October 1330, Montagu and his companions entered the tunnel, climbed up to the door, which had now been unlocked either by Edward III or a trusted servant, and overpowered Mortimer, killing Mortimer's personal guards. Mortimer was bound and gagged, led out of the tunnel and arrested, along with Queen Mother Isabella. Mortimer was sent to the Tower of London, and hanged a month later. Isabella of France was forced into retirement at Castle Rising Castle. With this dramatic event the personal reign of Edward began. These events seem to be echoed in an interpolation made to a metrical chronicle in around 1331, which describes the caves beneath the castle as having been carved out by Lancelot in his attempts to hide Guinevere from King Arthur following their adulterous affair. This seems to be the earliest reference to Lancelot and Guinevere's adultery that exists.