Hello,  These tubes depend in part on the capacitance coupling between
the 'current' in the tube and metal nearby to start.  Sounds strange,
but if you take a 4-foot bulb out of its fixture and hook up just the
end clips (and you don't electrocute yourself), you will find that it
will not light.  Sometimes it will start if you wrap your fingers
around the lamp near one end and stroke it quickly toward the other
end.  Especially in dry weather.  The bulb depends on being within a
half inch or so of the metal fixture.

Try this -- I use it in my piano.  Make a strip of aluminum (aluminium,
for those of you across the big pond?) foil about 1 inch (2.54 cm) wide
and slightly shorter than the glass part of the tube.  Tape it down one
side of the tube and the lamp should start.  I've also seen a piece of
wire wrapped spiral fashion for the length of the glass.  Don't touch
the contacts.

Regards,

Craig Smith