The castle was built in the Victorian era by the Marquess of Bute, a man that Ianto Jones said had lots of money but no sense. In the 20th century, a secret tunnel was built that lead to a bunker that could offer shelter during an air raid. The tunnel was infested with rats, which were later devoured by Weevils.
"Margaret Blaine" planned for Cardiff Castle to be demolished as part of the Blaidd Drwg project. (TV: Boom Town) However, although the nuclear power plant was built,[source needed] Cardiff Castle was still standing. (TV: Everything Changes)