Just doing some interior alterations and moved a ceiling pull cord switch. Very simple job, just three wires, all working after.
Then my wife switched on another light on the same circuit but it flickered and went off. The light I moved still worked though. Lots of fiddling later and I eventually took the ceiling pull switch off completely and left it with nothing working. Then it suddenly started to work again (apart from the light I had disconnected of course).
Any ideas? I am stumped.