Question regarding Side/Tail lights

Hi - I have recently acquired a 1984 Land Rover 900 and am having problems fixing an issue with the offside (drivers side) side/tail light. Simply put they don't work. I have changed the lamps and checked replaced the fuse. On inspection of the fuse board I can see a short wire connecting one side of the LH side light circuit to the same side of the RH side light circuit. I can't see this link on the wiring diagram in my Haynes manual, however I am a complete novice when it comes to anything to do with auto-electrics so it may be that I am not reading the diagram correctly. I removed the link and it didn't make any difference to the side lights and didn't cause anything else to break, as far as I can see.
So my question/s are
Is the link supposed to be there?
If it was put in by a previous owner, why would you do that

The PO may have put a link in to get around a power supply problem at the fuse box. A multimeter or a simple test lamp is your friend.

A multimeter is worth a shot. the simple lamp test is two spare wires attach to a bulb. Depending when the last owner had the Ninety for how long. He She or Alien would at some point replaced the light loom. Is the background where bulb goes in black or white. Black is the cheap replacement version while White is Original LR. Normally what fails is the solder, a little spring point for the positive part of the bulb to sit on. If the otherside working okay, then main loom is okay and only a replacement tail light with attached loom needed, as this just plugs into the main loom. They are easy to replace and they come with a fresh lens.
Hope this helps

does you fuse board look like this and the link you refer to feed side or output side

Yes it looks exactly like this, with regards to which side the link is, sorry but I have no idea

The good news is that the electrics on the early models are very simple. Are you sure that the tail light on the passenger side is working? If so, the fault has to be between where the rear loom enters the cabin (look for a little cover at the back of the tub) behind this cover on the drivers side, the rear loom is split between the left and right hand side. There's almost certainly a corroded connector in there - more likely several.

OK, that's my Saturday sorted then!
Many thanks to all of you for your help

Sounds like someone had botched a dodgey fuse, the left side and right side lights should be through a separate fuse .
If yours has the glass fuses, they are 5hite.
I had no end of problems with mine, which culminated with the fuse for the heater blower overheating and melting the fuse box.
The best way to cure it is to replace the fuse box with a later blade fuse type, that is not a fice minute job, but not as bad as it sounds if you can solder.
In the short term try cleaning up the terminals with a bit of sand-paper / emery cloth.

I had some funny stuff going on with break lights, indicators, etc, working then not, then working again.

Bulbs changed
then fuses ('85 110 so glass tubes) out and cleaned, plus the contacts. I did the whole lot with spray and a cotton bud.
Earths cleaned.

The Fuse cleaning worked wonders on most things, but in the end I needed new indicator housings, and one new rear light housing as the spring and the little plastic seat was worn and the bulb just would not sit right to make a good contact. Luckily they are pennies.

Thanks to everyone who responded. I cleaned up all the connections behind the cover at the back of the tub on the drivers and "Hey Presto" we have tail/side lights

Good job, but do get a simple multimeter and learn how to use it [ vid's on you tube ] Will be a useful skill to have for many things not just landys.