Eeyore wrote:

"Ron(UK)" wrote:

If the neutral wire isn't properly grounded enough voltage can be
induced by or leak from other 'live' circuits, maybe enough to cause the
fluorescent fittings to randomly flicker.

Ron, when the switch is off, there is no circuit. The neutral potential
literally doesn't matter.

Graham

Capacitive leakage from the HOT wire to the switch
wire? That could trickle charge and cause an
occasional flicker.
Random spikes would leak through much easier, and
cause random flicker.
Try as cure a small capacitor (100NF)across the
lamp terminals, just as long as the cap is much
bigger than the parasite one.