Blaidd Drwg (Welsh for Bad Wolf) was the name of a nuclear power plant, planned to be built in central Cardiff. Behind the plans was Blon Fel-Fotch Passameer-Day Slitheen posing as the new Lord Mayor of Cardiff, Margaret Blaine. The plans were to build the power plant on top of the Cardiff rift. The power plant would later have a meltdown, causing the rift to open. (DW: Boom Town) Many people became aware of this but were stopped by Margret, such as the architect who she ran over.
The power station since then has stayed in Cardiff. (TW: Everything Changes)