Ah, so its not just me who's had a look. I used a small open ender (6mm) to turn the vertical post past the stripped (I presume) area of worm. Just don't drop the spanner into the headlight assembly...
I suppose the next thing I want is a way of turning both the main and dip on at the same time...- or some crashbars and spots...
(Used to have the Australian spec twin main/dip headlights on my 748 so have some comparison)