STWNFI has what I believe is called a "Mother and Child" reading light.
She recently complained that it was messing about, going off with no
warning and not dimming properly.
I assumed the dimmers were the cause of the problem because at some
settings they worked.
We have a second one in our holiday let, so as no one is in there this
month I brought it round plugged it in and she was happy.

Two days later she complained the same was happening. Whilst playing
around with the dimmers thinking they were the fault again I heard a
crackling sound from the area of the socket behind a book case where the
extension lead used for these was plugged in.

Once I shifted the bookcase and removed the plug from the extension the
problem was obviously loose connections, all three screws hadn't ever
been tightened enough to even touch the wires, and the areas around them
were black.

Due to the inaccessibility of the socket this shop bought extension had
been there for several years but only now caused a problem. If it hadn't
been for the crackling noise I would be trying to replace the dimmers as
the lights worked fine with them on some settings. Strangely full power
worked better than reduced settings

Mike