We've just bought a bathroom wall light, (from Habitat), that claims
to be Class 2 and specifically says that no earth should be attached.
Looking inside I can't see how on earth (pun intended!) it can be
double insulated, and I believe it will be much safer with an attached
earth. The case of the light is painted metal, (aluminium), and
inside there are mains votage wires. i.e. The separation between the
mains voltage and the aluminium consists of the brown single layer of
sheath around the cable and then the paint on the metalwork. Does
paint really class as a layer of insulation for these purposes?

Anyway, not withstanding the above I'm going to earth the b*gger,
especially as it's in a bathroom, which brings me on to the question
of supplementary bonding.
I know this is a well trodden subject in this group, but I still need
a little clarification.
The wall light is going to be wired in 1.5mm^2 T&E that I've burried
in the plaster. I know it is permissible to use the CPC for
supplementary bonding, so I presume this means that I am OK bonding
from the JB in the loft, (that feeds this light), onto all of my other
supplementary bonding?? Is the CPC in 1.5mm^2 suitable for this, as
I've read talk of min 4mm^2 for supplementary bonding???

Finally, if I do have to run in a separate supplementary bonding right
to the fitting, is this OK to run in the wall cavity, (as I forgot to
plaster one in the wall!) - Hopefully this will be irrelevant anyway,
as someone will tell me that the JB in the loft, being in 'close
proximity' to the wall light, is a suitable place to bond to.