My 2012 Westminster is getting condensation inside the perspex. I seem to recall reading that this is normal as the lights breathe to allow water to drain if the car has been wading. Am I correct or should I be looking for a blocked drain hole or a failed gasket seal?
Grateful for any advice.

remove the light (very easy to do just 2 hex bolts inside the tailgate).

At the back you will see a grey plastic cap over a spout/hole. This is the breather. Remove it and drain as much water as you can using gravity. Then get a hair dryer or low oven to dry out,

Replace the cap (loosely) and re-fit. it will reappear from time to time but that's the nature and bad design of the beast.

Seal the join where the clear meets the backing if the join has come adrift as mine did.

Thanks for the comments. It sounds like the same issue I had with an F30 335d BMW. One of the rear clusters had this issue and I used to remove it and set it on top of a dehumidifier for a couple of hours and then refit it.

Yes, a night in the airing cupboard used to sort mine out on the occasions it happened... It seamed weather would start it off, the more water got in, the more it would attract! Very odd UK weather...

It's reassuring to know that it isn't just me having the problem Craig.

No no, a very common problem sir... Just been splitting apart a set of DB9 rear lights to re seal them as Aston Martin chose to seal them with something that resembles nylon! Weird...

You would think Aston could come up with a slightly more suitable product to use as a sealing product Craig.
I guess they expect owners to simply return the car to the dealer to get the problem addressed.

Baffles me sir...