I've checked that my problem is not a duplicate of this
Electricity passes through a bulb holder, even when the switch is off because I don't have a backlit light switch.
The kitchen light fitting, below the bathroom, got flooded with water, water was pouring through it. Naturally this tripped the breakers for the downstairs lighting circuit.
There are 2 light fittings on the kitchen light, only one got waterlogged.
The bulb has been removed, and the light switch is in the off position, but the breaker for the whole downstairs light circuit won't let us turn it back on - when we do, there is a spark from the fitting, and the breaker goes off again. Clearly, there is some current passing through it, but why?
Does this mean that the fitting has been wired "Backwards"? i.e. the circuit goes live --> fitting --> switch --> ground?