Think I need to change the bulbs on the Shag, guess there are original. Usual tired HID symptom of seems bright enough, but no illumination.
Trouble is, I think the bumper has to come off to change fikkin bulb.
Blimey. Quick google can’t even find much detail on it, only one small video and it does show the bumper off. 
Lack of technical forums and complicated jobs really is pain for newer cars 
There is actually an EU law that any bulb must be changeable by a reasonably capable member of the public at the side of the road using the supplied toolset within 15mins.
But Audi exploited a loophole, that many others followed, by making it a "dealer only" change, they do not have to comply.
As all XJs have HID bulbs main bulbs and LED sidelights, they can genuinely claim it is "dealer only". Obviously, HIDs rarely fail (they just get shit with age), so its probably not deemed a biggie.
The only owner changeable bulb in the X351 XJ is the numberplate bulb. Everything else is HID/LED, and probably fikkin' expensive.
Audi were pushing their luck a lot, as anything in the rear light cluster was claimed by Audi to be "dealer only", even though every bulb was traditional filament type, thus could blow at any time. But what else would you expect from VAG?
Not looked, but I reckon I can get away without removing bumper...