On Monday, 19 March 2018 20:49:51 UTC, TheChief wrote:
...There appears to be some twin and earth heading
from the switch in the general direction of the dud fitting. The
daft bit is how the dud fitting is fed. A ceiling rose attached
to the original ceiling has drop flex passing down through a
lower suspended ceiling into the dud light fitting.


I had one of those.

2-core flex feeding a class 1 luminaire with no IP rating in Zone 1.

Owain