Just replacing a bathroom light fitting. Running from it in the opposite direction to the standard 1.5sqmm T&E supplying it is a single core 1.5sqmm red cable (proper PVC outer sleeve and everything). This connects to an extractor fan, providing a live connection switched by the light switch. The light circuit is part of a 10A light circuit, eminently reasonable so far. However, the fan is also supplied with its only neutral and a permanent live connection from a fused (13A) but unswitched spur off a nearby socket circuit.
Don't ask me how I know, but this is an electric shock risk (fortunately only to parts of one hand owing to good self-training).
Does anyone think this is a good idea?