Part of the Elan Aqueduct (nprn 95469), itself part of the Elan Valley Water Scheme (nprn 96459), the Gwernaffel Conduit carries the aqueduct over the Gwernaffel Brook to the south-west of Knighton. It is some 65m long and at its western end joins with the north-eastern end of the Knighton Tunnel (nprn 412103).
B.A.Malaws, RCAHMW, 16 November 2010.