Disco 1 200 TDI steering box

So i have just spent a couple of evenings on here looking at steering box threads but not really found the answer to my question.
My steering has a lot of free play before anything happens i would guess 40 to 50 degrees.The steering itself is fine after this no noises and lock to lock ok.All linkages etc are fine it is def freeplay in the box. I have read about adjusting the locked allen bolt on the top but would this cure the freeplay before anything happens. I suppose i am being picky really i just want to know what this adjustment actually does.Can anyone explain it for me.
Cheers in advance

You could do a body swap to a fender and all would be perfect

Alternatively

Get someone to wobble the wheel and inspect all the linkage and the rubber thingy, more likely to get wear there tbh.
Linkage is just above the box

I can rotate the input shaft by hand in the engine bay