Fed up with this happening regularly, I decided to do something about it this morning.
I never liked the idea of drilling holes in the front as I think water and dirt would get in too easily.
So I decided to take the lights out, it's so quick and easy, 2 screws and pull, and drill a hole underneath. I think it will be less susceptible to water and dirt getting in. The hole is at the bottom underneath the side reflector. It's a 2mm hole.

Click image to enlarge

Click image to enlarge

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If it is still relatively accessible (the hole) then you could get/make a small silicone or rubber plug. Stick it in and when you have condensation issues, pull it out for a day or night and then back in again. That way lot less risk of water and dirt getting in  MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

The above is the solution I adopted about a year ago albeit with 3mm holes.
Been very successful to date, no re-occurence of the dreaded condensation.

Good stuff. I thought I would go 2mm first and if they blocked up or did not offer enough ventilation then I would go to 3mm. Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

please forgive my ignorance as ive not played with a rear light yet (still need to buy a RR!) but isnt there enough room in there to leave a silicon pouch thingy (like you get shoes/laptops) in there somewhere?
I had the issue on a Passat headlight a long time ago and that sorted it out for me...

Unless im being stupid (quite a possibility too!)

^
Pami.. It's a sealed unit. The seal goes eventually and lets moisture in. I have read of people running araldite around the seals again but I hope the hidden hole will do the job.  Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

Don't know about a 2006 light but the earlier ones are provided with ventilation and still condensation forms. They are not sealed units.
The drain holes drilled in the bottom simply allow any rain water that has leaked in by way of the inadequate perimeter joint to drain away and also provide a nominal improvement in ventilation.
Although the body of the units are ventilated, the effect of this is minimised by virtue the large void behind the clear outer side/rear is only connected to the ventilated space by a small perimeter gap round each of the red/amber lenses.
Resealing of the perimeter joint with Araldite will certainly have the effect of reducing condensation but will not reduce it completely.
Even new units, perfect in every way, will still suffer nominal condensation due to the ever changing atmospheric conditions they are subject to. In this case however the ventilation provided undoubtably helps to keep the units clear due to temperature changes and external air moisture content.
Plastic light fittings on cars have always suffered condensation but previously light fittings tended to be constructed from thick red or amber plastic which tended to hide the condensation.
Modern "clear" light fittings have added to the problem as you can now see the condensation.

^
I agree, I have just had a brand new front NS lamp cluster fitted, it still fogs up at the bottom and that is straight out of the box. There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
KIA E-Niro 4+
2021 Discovery 5 D300 MHEV commercial

The 2010 rear lights can condensate as well , what a pain  1990 3.5 v8 defender
2000 4.6 v8 30th anniversary prins lpg
2004 4.4 v8 vogue prins lpg
2011 4.4 TDV8 Vogue
faultmate extreme
rsw allcoms
Autel 906BT
Gap iiD tool

The headlights have breather tubes on them, I assume to allow for the expansion of the air due to the heat of the bulbs. That of course draws moist air in when the headlight cools. Taillights should have virtually no heat at all due to the LED lights but still sunlight will warm up the insides quite a lot, raising the air pressure. I guess that even time, that "fatigue" of the plastic, plus UV radiation (degrades almost all plastics) will form cracks in the plastic and or joints, causing air to be able to go in and out. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

This has been a constant problem on these vehicles and is well known to Land Rover Ive authorised lots of these to be changed under warranty without any come backs, even been able to get vehicles out of warranty done provided therer was no damage and they haven't been tampered with.

Can the light units be opened up at all - can drill the hole but can see staining where condensation has puddled inside. 17 MY Corris Grey 4.4 VAB
Silver MB R231 SL350

No sir... The 09> headlights are sealed with an un-meltable glue & the rears are sonic welded together so NO they won't come apart with ease...

Doh! I suppose I should have guessed that it was easy and logical then LR wouldn't entertain the idea..... 17 MY Corris Grey 4.4 VAB
Silver MB R231 SL350

Rumour has it they can only be opened in the Cotswolds some sort of mystic magic  Present :2008 TDV8 HSE
Gone Audi A5 2.7TDI
Gone Discovery 3 HSE
Gone Mercedes CLK
Gone Range Rover 2.5 DSE