[youtube=http://www.youtube.com/watch?v=5GWUhxr7cCA]
Do you remember the scenes from The power of three? The Doctor and Amy are summoned to the UNIT headquarters under the Tower of London where a Kate Stewart shows them several cubes under investigation, every single one behaving in a different fashion. The Doctor recalls his friendship with Kate’s father, Brigadier Sir Alistair Gordon Lethbridge-Stewart.