To add to the stories on strange substitutions.....
Somewhere in the 50's my cousin was a mechanic working in the Army in
Egypt. Their lorry got stuck way out in the desert. He did his mechanic
thing and found that the condenser (capacitor) in the distributor was duff.
Naturally no spares were at hand. My cousin told me he took out the tail
light and then connected the wire at the bulkhead end to the condenser
connections....and away they went! He maintains that the capacitance of
the length of wire used to connect to the rear light was sufficient.
Hmmm, always wanted to check this one out on an old Army lorry.