Land Rover Repair: No head and tail lights on my Defender Td5 2000, fuse box, defender td5

Question
For whatever reasons I suddenly my head, side and tail lights stopped. Fuses are ok, brake and indicator lights ok.
I measure something (+/- 11 volts) at the light switch but that gone as soon as I use the switch. I only get access to a 1999 and a 2002 wiring diagram but both are not completely similar to a 2000 defenders layout. I think it has perhaps something to do with the dim/dip relay but I can't understand why even without switched ignition key thing are working as it should.... Can you please help me out??

Answer
I suspect the root of your problem is corrosion in the fuse box.  Remove the box and check for burnt or corroded contacts, and do whatever is necessary to ensure that you get 12v at the switch, and it remains when the lights are switched on.

The problem is either in the fuse board or the wiring itself