Query

If you clamp it around only the neutral you should read the same amperage. If you clamp around the phase conductor and the neutral at the same time you will read zero.

If you clamp it around the neutral conductor, you will get no reading. When the current from the phase conductor flowing through the element of the bulb and because of the resistance in the element, the current will be restricted by the element resistance and causes the element to generate heat. The heat is then converted in to light. All the current will be used up by the element. That why, the neutral conductor will be zero.

You will not able to get any current at the neutral conductor.

Are we missing Kirchoff's current law?

The Post #1 is correct, the phase current and the neutral current will be equal in a single phase circuit. (the same is not true for a multiphase circuit of course)

Unless some one has connected the load across phase and earth of course (and you don't have the Earth fault MCB at your home switchboard)

Simon... current flows from the source to the load then from the load back to the source. Current is not consumed.

So, why does the lamp go out when the neutral conductor is disconnected from the supply, then?

How many conductors run to your 240 volt light? Three or four? What is the nature of the system? Is it a standard American/Canadian 120/240 volt single phase 3 wire consumer service?

If the system is a standard 120/240 volt 3 wire service, you should have two hot conductors, lets call them L1 & L2, and a bonding conductor going to your lamp. In this setup, there is no neutral connected to the lamp. Current on L1 & L2 should equal each other as current flows from the system source to a load then from the load back to the source.

Please describe the system type and the number of conductors going to the lamp.

What ever may be system, the tong tester or ammeter connected to any one side of the device( source side,return side) should show the same current.

Obviously...

I asked for the nature of the system to try and reason why he sees no current on the "neutral". About the only way it make sense is if, there are four wires going to the light, two hots - a neutral (that is not used) - and a bond wire.

measured current will not change , may you measured volt ?

if it's so, it will gave zero reading for neutral.

One of the possibilities that there is no current in the neutral conductor is that the return path in the posted case is via the earth conductor. Never do this! The earth conductor is there for personal safety and should never carry current except under fault conditions while the circuit protective device operates.