Dark Light Dwellers (UN-D-7983)
Enticed across the barriers towards the extreme energy production of the Calder Hall nuclear power plant, the creature unwittingly found itself in the main reactor where it's presence - due to it's unique form- caused the reactors to approach super critical levels.

Fortuitously the Daemon chose to return to it's own dimension moments before the reactor's temperature exceeded fatal levels.

Had the Daemon not, scientists predict that they were less than one minute away from a fatal meltdown that would have scattered toxic radioactive materials over Northern England and Scotland. A disaster that would have taken affected areas centuries to recover from.
(See evidence)