The bishops took possession of the castle later in 1271 and promised Llywelyn that building work would temporarily cease and that negotiations would begin the following summer. In February of the next year, however, de Clare's men seized back the castle, threw out the bishops' soldiers, and de Clare – protesting his innocence in these events – began work once again. Neither Henry nor Llywelyn could readily intervene and de Clare was able to lay claim to the whole of Glamorgan. Work on the castle continued, with additional water defences, towers and gatehouses added.