The texture on the underside of the shade of the hanging spotlight (HangingSpot in the Object Heirarchy) is not illuminated, but clearly it should be (compare it with HangingSpotFlush).
Fixing this oversight was quite simple; I applied an illuminated material to the underside of the shade. The image below shows the difference between the original and the new:
You can download the fixed version of the model Here
Create a folder called obj
in your Thief installation folder (unless it already exists) (e.g. Thief2\obj\)
and extract into it the file ELECSPOT.bin
(For Thief 2 you can get nicer versions of the lamp-glass texture
Here)