 The castle was besieged the next year by Owain's son, Gruffudd, but the castle was relieved by an English force sent by Prince Henry.By 1538, Grosmont Castle had fallen into disuse and then into ruin; a 1563 survey notes that its bridge had collapsed and that, although the outer walls were intact, the interior was in decay and its building materials inside had either been removed or were rotten.A 1613 description noted that it was "ruynous and decayed".