Shallow Fog - Approach Ban

[ATRflyer]

Hi all,

Just wondering if anyone can help me out with this question. If there is a very shallow layer of fog over part of the runway and the airport is giving RVRs below CAT I minima; can anyone confirm that the approach ban does still apply, even if an aircraft were to call runway in sight early on in the CAT I ILS approach?

E.g. An aircraft 20 miles out can clearly see the runway threshold, all the approach lighting and the majority of the area around the airport, and calls visual. The aircraft is then cleared for a visual approach by ATC. Just want to confirm that the approach ban does still apply requiring at least CAT I minima (i.e. 550m in the touchdown zone); or is the minimum required touchdown zone RVR now 800m, since the aircraft called 'visual' early on in the ILS approach?

I presume the approach ban would still apply as RVR is always the main thing taken into account. Obviously you would either not commence an approach, or if you did; make a go-around at the outer marker unless the RVRs improved prior to reaching it. I am a little unsure though as to whether the minimum required touchdown zone RVR, in this example, would be 550m or 800m?

Many thanks,
All the best,

Atrflyer