Black Mountain South Top
It is a top which falls exactly on the Welsh-English border , straddling Powys and Herefordshire . 
<triplet> Welsh <subj> English <obj> shares border with <subj> Powys <obj> contains administrative territorial entity <triplet> English <subj> Welsh <obj> shares border with <triplet> Powys <subj> Welsh <obj> located in the administrative territorial entity <subj> Herefordshire <obj> shares border with <triplet> Herefordshire <subj> Powys <obj> shares border with