3 AG1 cells (wrapped in insulation tape and which are the smallest you can get easily) in the vent tube, which was turned to make the top plate a collar and extends to form a push-fit in the base (from two bits of 3/8" angle).

The LED is from a cheapo cupboard light which had some 20 LEDs for a few quid. The LED is very stubby in shape, which is ideal as it allows the wires to be bent, one contacting the case, the other turned back on itself as a spring to contact the end cell. No resistor as the interbnal resistance of these small cells limits the current – still very bright though!

No switch- just push the top into the base.

I spent ages wondering how to fit 3 cells and LED into the body, then I found the AG1s and realised how small they were. The cap is drilled letter K by the way and is also a neat push fit on a Crayola pencil

Seems a shame to paint it black now.

Neil