Dame Helen Mirren returns to the Wizarding World to oversee this head to head wildcard match up. The two houses that lost their previous battles in this distinguished TV event series now have one last chance to take their place in the grand final. There will be special celebrity guests, actors from the original films and more Harry Potter trivia than you could squeeze into a cupboard under the stairs. Tonight's episode is another magical Harry Potter chapter of Drama, courage and redemption.