Must be a little bit of heat generated in theat 500 Ohms resistor.
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It does get fairly warm but the heat is spread out over the 2' length. It calculates to about 73W. However, if the starter shorts out and the lamp is left on it would be about 115W.
This example was made in Australia by a small appliance company in Melbourne by the name of 'Companion'. They call this light a 'Flurinstant'. I'm pretty sure it was originally a UK design however. The instruction manual also mentioned a 40W and double 20W version.
Many years ago I remember seeing homemade versions of this in a car park in an old part of Sydney. However, an incandescent bulb was used as the current limiter (240V 100W gives the right current for a 20W tube) and they were all assembled hanging together with bits of wire plugged into the BC sockets. One day I'll reproduce one.
