Star Whale
The Star Whales are an ancient species, but by the 29th century they are believed to be extinct, save for the one seen in The Beast Below (Series 5 : Episode 2). The Star Whale was drawn to Earth by the cries of children when Earth was facing destruction from solar flares. The humans of the United Kingdom captured the Star Whale and tortured it into moving, becoming the space craft on which the United Kingdom escaped Earth on (for they built the city on the Star Whale’s back). The humans worried that if they freed the Star Whale, the city built on its back would be destroyed and kill everyone on board. So the British Government fed anyone who protested this into the Star Whales mouth for it to eat, which it gratefully did, providing the human was adult. If it was a child, then it would refuse to eat it.
When the Doctor arrives on the Starship UK, he is faced with the decision to save the Star Whale and kill the humans on board, or save the humans, and kill the Star Whales conscious mind, so that it wouldn’t feel pain any more. However Amy rescues both, when she notices that the Star Whale plays with the children, and points out that the Star Whale came willingly to Earth. She forces Queen Elizabeth the Tenth (Liz 10) to abdicate, stopping the torture of the Star Whale, which then increased speed as it was still willing to help the humans.