A short stretch of the [Glamorganshire] canal escaped the building of the A470 between the Prince Llewelyn (now an enlarged private house) and Pontydderwen canal bridge (standing). Here the Cefn Glas overflow weir and the remains of Cefn Glas colliery can be studied along with the tunnel taking the Taff Vale Extension railway through to the Cynon valley.
(A Guide to the Industrial Archaeology of South East Wales, AIA, 2003)
B.A.Malaws, RCAHMW, 29 November 2007.