As discussed earlier - the sunroof drains on the 405 and 494 have a well known nasty habit of rotting out.
Mine is 4 years old so expected it all to be tip-top in there but no, got in there with a cheap endoscope and I have the early signs of rust too.




Watched some videos and formed a plan.
Bought some stainless steel 10mm pipe stiffeners from ebay and some epoxy glue from Amazon



 2021 L494 D300MHEV Autobiography
2019 Discovery Sport D180 HSE

So first step is the scariest, access.
Open the roof, get your fingers under the panel and tug up hard. It comes off pretty easy really. Once started, just work your way to the back. I found closing the roof once it was started made it a little easier to get your fingers in.

It's just a simple channel with some spring clips that grab hold of it and its aluminium so no worries about snapping it.








Clean the drain as best you can, blather the pipe insert in as much epoxy as you can and drop it in the hole. The top edge of the stiffener will sit above the hole and then spread a little extra epoxy round the edge to seal it in. That's it - done.








Then carefully position the trim back in, wedging the outer side in first and push down. Will just snap back on.

Hopefully, with the affected steel protected from the air and moisture by the epoxy and the water pouring down the stainless steel insert, any corrosion should have been stopped in it's tracks.

Whole job takes 20 minutes and if you plan to have a 8+ year old 494 or 405 with an opening sunroor, it WILL save an awful lot of heartache and cost. If you can't face doing it yourself, maybe pay your mechanic to do it? Would be an hour's labour well spent IMO. 2021 L494 D300MHEV Autobiography
2019 Discovery Sport D180 HSE