Tweaking some lighting, I turned off the mcb for the LX circuit and
opened a pendant fitting. Double-checked with a neon 'driver - not live,
is says. Unscrewed one of the neutrals. As I do so it sparks quite
impressively. Why?

(I chickened out and turned off the whole house supply in the end. Wife
really enjoyed that on a Sunday evening...)

It was a pretty common pendant arrangement - four cables - incoming
L/N/E feed. Outgoing feed. Cable to switch. Cable for pendant fitting.


A spark must means there's current flowing - but where from? I did
wonder whether the 12v transformers for the halogens might have caused
it?