Would anyone know what this brown wire is for, it has a permanent 12v going to it but all my lights etc work at the back, it's a 1970 series 2a 109 ex military
If the wiring harness is standard then refer to the wiring diagrams on this forum.
I'm not familiar with military wiring, but that does not look original to me. Are we looking at the lighting connections in the RH rear corner? There isn't normally a brown wire back there. Brown should be a non fused 12V supply. It may be something a PO has wired for a caravan feed or similar. On later vehicles like Defenders, there is a purple wire in the tow electric circuit which is a similar 12V feed.
I got the wiring loom from autosparks to suit my series
I forgot - military wiring... There is a brown red wire which is an auxiliary feed for the NATO socket.
Perfect 👍