Both lower brake lights failed at once

Mick was spot on. I went under the car, pulled down the wire coming off the body (it has a rubber plug on it to seal up the hole, but it came out without problem as the rubber is still soft) and discovered that sometime during the car's past the + wire for the lower stoplights was poorly repaired. Apparently someone has forced the plug and managed to strip the wire out of the plug, then bypassed the plug for this particular wire using a small indoor connector.
Of course after some good years (I've had the car for almost 9 and this was done before I got it) this little indoor connector was rusted solid. I wiggled it a bit and the brake lights started working again, so I'm going to use the soldering iron and heatshrink tubing, plus a pair of bullet connectors to do a proper job.

Thanks again for the help, saved me a lot of guessing

P.S. If anyone needs the info, on lwd cars the connector for the bumper loom is also at the left side, behind the wheel arch.

Good job. How was the rest of the loom that runs the length of the bumper? Mine was disintegrating and all the connections were corroded. Worth replacing/repairing whilst you are on.

Actually it looked unexpectedly well Too bad that after I put everything back in, the left turn signal started to go twice as fast :lol:

Had a look at the bulb, appeared to be OK, emergency signal flashes at normal speed so the relay is OK. Obviously the back bumper loom has more damage to it.

At this point I cannot describe how unattractive looks to me the idea of taking down the back bumper, but I may have no choice if the turn signal wire is broken somewhere inside it's plastic sleeve.

It takes less than 10 minutes to drop the bumper down.
The only problem area is the 2 upwards screws in the bottom edge. These seize and snap off, so the broken parts need drilling & re-threading.

You will also need to allow some time to treat the corrosion revealed in the bottom corners of the wings

Yes, I know, that's why I'd rather avoid dropping the bumper