White sleeving, all 3 are insulated and covered by grey flex.
So, would you say the white wire is
a bare wire with a loose white sleeve over it
or
a wire like the other two with 'proper' insulation?
Is the cross section of the cable circular, or more of a flat, lozenge shape?
Wondering if it is flat cable and during remedial work the bare earth has been sleeved with some alarm cable sheath or similar.
Or is it possible the black core is actually blue, and its wired in old red, white, blue 3 core?
Do you think the cable actually is rubber?
Is the sheath actually grey?
Or a matt black?
It's not unusual for 50s or earlier lighting cables to have earth in them.
Are the switches round, or do they have wooden back boxes or something else?
A few photos of inside some random switches or roses or sockets would be very interesting.