Faulty LED

[David Cochrane]

So Herbert did it all wrong then? And I've done it all wrong again? All cars on the roads, then and today, use the body as an earth return. If done properly there is no problem in my experience.

I'm afraid that he did! It's cheaper to use the body as an earth return than to fit separate wires. Also the modern monocoque body is much easier to use an an earth return than the collection of parts which make up a pre-war body. Bulb-holder / reflector / headlamp body / headlamp bracket & bolt / wing / flitch plate / body / battery cable - what a lovely lot of joints! And their surfaces are either painted or rusty (depending on the state of the car) but neither of which are particularly good conductors. Go on - fit earth return wires and bypass all those interfaces!