I've always thought that it's a pretty cool thing and yet cruel that the Series 2 4doors don't have the same setup. It's a badge stuck onto a thinnish panel, not hollow.
I think there was a factory option on sedans but not sure if Series 1 or 2. Slightly different garnishes.
S2 is like this.
I will try to do it oneday though. (I have a spare series 2 Garnish)