WARNING! SPOILERS: This post contains spoilers and speculation for the Doctor Who series nine episode The Husbands Of River Song. After the bleak midwinter of series nine this years Doctor Who Christmas special is like a beacon in the dark. Alex Kingston and Peter Capaldi sizzle with incendiary energy as they weave their way through the action while never straying far from each other. There is a joy in their performances that keeps the comedy fizzing and imbues the ending with a bittersweet air that in less sure hands may have turned maudlin. If this is River Songs final appearance it is a fitting one. It is lovely to see the character given another chance to shine as she and the Doctor race from one adventure to the next. We are indeed reminded of what a bad girl River Song truly is but are not allowed to forget her underlying vulnerability. Her love for the Doctor is both her strength and her weakness and Alex Kingston is superb at playing both sides of the coin. Peter Capaldis restrained reactions are beautiful in their subtlety, his exasperation and tender feelings for his wife understated but quite clear. Each roll of the eyes and admiring glance adds to this madcap story that ends on a moving note of love and loss.