This railway inclined-plane was built in 1832-34 by the engineer John Brunton as part of the Claypon's Extension Tramroad of the Brecon Forest Tramroad from the Swansea Canal at Gurnos and the Ynyscedwyn Ironworks over Mynydd y Drum to the Brecon Forest Tramroad near Onllwyn. The incline went out of use in the 1860s ans most of it survives as an earthwork. Published as part of Stephen Hughes, 'The Archaeology of an Early Railway System: The Brecon Forest Tramroads' (RCAHMW, Aberystwyth, 1990).

Stephen R. Hughes, 07.09.2007.

The incline includes the following monuments:

* Under-bridge (SN 7884 0975): this is a
small bridge with a segmental arch over
Nant Gyrlais (Fig. 58).

Over-bridge (SN 7900 0970): destroyed (Fig.
58).

* Under-bridge (SN 7933 0962): this is an * Reservoir (SN 8018 0944): slight banks
accommodation bridge with a semicircular (Fig. 59).
arch (Fig. 58b).

* Stables (SN 8010 0940): grassed foundations.

** Winding-tunnel (SN 8011 0942 - 8012 0942): partially blocked (Figs. 58-9).

Two limekilns (SN 8006 0939): rubble mound

** Engine-house (SN 8013 0942): ruinous
(Figs. 58-9).

Look-out hut (SN 8005 0942): destroyed