R129 - Damp footwell

[GreenVault]

I noticed over the w/e that the carpet in the driver's footwell of my Sl500 was very damp. I have a vague recollection of reading that there is a drain that can get blocked by leaves etc leading to exactly this problem. Does anybody know whether this is correct and, if so, where the drain is so that I can unblock it? If not this, any other likely causes? It has the hardroof on at the moment, and always has a lot of condensation on the inside of the windows if left out overnight. Could these problems be linked?

Many thanks,

GV