Cathal is a multifaceted character – an estranged and lost child, a reflective soul, a self-destructive drug addict and a loyal friend. He is very central to the story, even given his little association with Jules – and Colin Morgan played this delicate fragile character of many aspects with much sensitivity and charm. Without a doubt, the final act of his performance was heart-wrenching, moving and stirred so much empathy for Cathal that it almost became unforgettable.