Thames River Monster

The Thames River Monster was a creature of unknown origin that was chained underneath the Thames River by a wealthy business family in the early 1800s and was the cause of the river's periodic freezing. The main reason for the creature's imprisonment was the business family's discovery of how the creature's dung could be used as a superheating biofuel. The creature also had a symbiotic relationship with various smaller glow-fish in the river who fed the it by melting the ice under those unfortunate enough to stray alone on the ice of the Thames. In 1814 during the last great Frost Fair, the creature was eventually freed by the latest generation of the business family's legacy: Lord Sutcliffe, thanks to the help of The Doctor and his companion Bill Potts.

Appearences

 * Doctor Who (revived): Season 10 Episode 3 "Thin Ice"