Electric light

As Blon Fel-Fotch Passameer-Day Slitheen removed the skin suit of Lord Mayor of Cardiff Margaret Blaine from within the ladies' toilets, Cathy Salt noticed the characteristic blue glow and asked if there was something wrong with the lights. "Margaret" claimed that they were always "on the blink" and she could not say how many memos she had sent. (TV: Boom Town)

The lights in LINDA's base were switched off as Victor Kennedy, actually the Abzorbaloff, arrived via the lift. By raising his arms and exclaiming "lights!", Victor switched the lights back on. (TV: Love & Monsters)