The day before yesterday our stairhead light stopped working. So yesterday I changed the bulb. Still didn't work. Got my multimeter out and tested the terminals on the fitting. Stone dead. Took the covers off both switches (downstairs & upstairs) and tested the terminals. Stone dead. All the other lights on the ring were working but anyway I checked the fuse in the consumer unit - OK. Put it all back together and prepared to take up the floorboards this morning to trace the broken connection.
This morning the light was working again. Quite steady, no flickering as if a bad connection had temporarily touched again.
Took the switch covers off again. With the light switched off, the voltage between N and L was 230-250V - but not steady. Instead it was oscillating between the two extremes at about 2Hz, regular as clockwork. Anyone know what is causing that? Might it be related to the transient fault?