Dodgy cable joint.

Here you see part of the old rubber braided lighting cabling botched up to a newer section when a dividing wall in the kitchen below was removed in 1978, meaning that the light switch had to be moved as the wall it was mounted on no longer existed. As well as being safer, I'm sure it would have been easier to use a junction box! The grey twin & Earth is it's replacement in 1988. I only came across this today as I had to remove floorboards to replace an old leaking lead water pipe