I’ve recently done quite a bit of work under my L405, but I can’t work out what this is, any idea?
Can’t find anything in the WM above for the item marked in yellow.

Big empty plastic box. Presumably for aero or NVH

Yes as Mike’s has said. It is simply some plastic trim to provide improved aero under the vehicle. It doesn’t have anything behind it that it protects etc. I took all the plastic off a few weeks ago to clean and then apply Lanoguard. One thing these plastics do is trap loads of mud and stones etc.

Thanks guys, riddle solved!
The only thing I could find in the WM was that’s the location for the HV battery in the hybrid models, I did wonder if JLR had a mix-up on the production line for a moment!  V6 Vogue - “Less is More” - less to go wrong!