Mystery fault in a trailing socket - what caused it? There appears to have been an arc (electrical spark) across the Live, Neutral, and Earth connections. Extra is a close up that shows where the brass has melted. Must have been very brief, as the plastic hasn't melted. Only possible cause found, was a loose Neutral connection in the plug.

Vapourised metal in the cover was cleaned off, and the unit tested okay. Nothing of note happened (...or Blipped) today.