Lightings and the like agree but this was common as in post 1 in industrial set-ups and I've seen it often.
Bad practice and poor design at most but this set-up is seen under different circumstances as been ok ...I.E. a conduit through box with a clicks unit attached may have other circuits running through behind the click outlet. Any Electrician worth even a small part of their competence would know isolating the outlet may not isolate the wiring running through.
I obviously wouldn't do the OP example myself but other than been a bit rough where exactly is the risk, maintenance, testing and fuse replacement should be done by a competent person and they should recognise the wiring in the back may not be associated with the Sw/fuse.
This is also seen when running pipework through say a multigang grid switch with say a socket circuit running through through the back of the switch to an outlet nearby which again is common saving time and materials and may look better than multiple pipes.
A light fitting as mentioned is the actual a accessory 'load' and deffo a no no to using as a throughway for other circuits as would be a storage heater or shower unit well you get the picture.... you could always put one of E54's favourate solutions on it 'A STICKER'
- caution contains multiple circuits....
Ill stand corrected if you get dig a regulation out but it would have implications on the acceptable examples Ive given.
