Something that is possibly of significance is that Black Rock does not appear on Ordnance Survey 1:50,000 mapping data. Whether this is an error or otherwise I do not know. But it certainly seems to be an anomaly since other islets, large rocks etc do appear. Even many small rocks that are entirely submerged at high tide appear, never mind a large rock with a lighthouse and structures on top.
I imagine 1:50,000 OSI mapping is one of the layers available for a moving map display in addition to nautical charts etc in this context. Hopefully, this anomaly is not of any relevance but it is certainly concerning in any case.