The part number I bought is 4H0853738T94.

https://i.ibb.co/hgcWcNn/20240729-202242.jpg

That looks like it's designed to just clip in. Is the single shorter protrusion some sort of release latch?

Good question. I'll give it a closer dose of looking at.

The manual makes reference to two retaining clips (8L0807180), and that's the awkward part of the exercise.

I tried a dry-fitting just now prior to going anywhere near it with clips, here's a video of it. I can't get it to settle into where I think it should go.
I'm trying it in this position because if you notice on the grille, the badge has two notches to help it locate, and the vertical black strip on the grille has a small raised notch likely used to locate it vertically. I just can't get it to sit right.
Here's the video; https://youtu.be/4u_mRppsF-I?si=XCl5KtSnvnPvFndy

I wondered about that mesh in a previous post, especially since the parts catalogue doesn't show it, nor does the PDF. Has the mesh been added, and in the process, made it impossible to fit the W12 emblem? Is that perhaps why it didn't have one?

I don't have a clue about the mesh. Is it not standard? However it doesn't stop the 'legs' going through the mesh, it just doesn't sit nicely anywhere.
Maybe it's a W12 thing?

Firstly, apologies as I apparently gave you the wrong part number (4H0853736A).

This bit about the mesh got me thinking again, and I started reading through all the posts again after watching the video, and although I saw your post (#11) where you mention the part you bought (4H0853738), it appears we both got the wrong part numbers.

The part number I gave was for a 2010-2013 D4, where there is no mention of the mesh in the parts catalogue. Yours appears to be a later model D4, and, when I look at the W12 grille, it does indeed have a mesh. However, the part number is different yet again, this time 4H0853738A. I don't have a picture of it, nor does the parts catalogue show it to be a superseded version of the one you bought (4H0853738). Nor sure where you purchased yours from, but if buying the other one, I'd get photos of it beforehand to compare with yours. There is still the fact that the two clips are still part of the problem when it comes to fitting.

Lessons learnt from this:
1. The PDFs 'may' not be 100% correct if the model (D2,D3,D4) has gone through a facelift during its lifetime
2. It pays to have you car details in the signature line to avoid confusion like this

Thanks very much for the replies. I have started the return process for the badge I currently have and they have sent me a link to the correct one.

I've updated my sig to show that it's a D4, thanks for the tip.

Glad that you can still return the badge.

As for the signature, add the year as well, as that is the important part.