Doctor Who: The Doctor, The Widow and The Wardrobe Prequel

Overview:

The Eleventh Doctor has his hand on a button that, when released, will blow up a ship that's about to destroy the Earth. He calls Amy Pond on the TARDIS phone to ask her to rescue him, but realises she can't fly the TARDIS, he doesn't have the co-ordinates to give her and she left the TARDIS long ago. The Doctor admits he just wanted to chat, says "Merry Christmas, Amelia", and releases the button. The ship explodes.