Brynwern bridge was built in 1885 and erected by W Clifton-Mogg and S W Williams, engineer. It was made at W Thomas' railway works at Llanidloes. It has now been demolished, with some pieces remaining at the site as a display piece.
It was a three-span iron bridge of three pairs of wrought-iron lattice girders forming through trusses, supported on pairs of triple cast-iron columns resting on masonry piers. There were truss braces each with a star-shaped devise on top of the triple columns and against the balustrade. There was also a deck of iron plates reinforced beneath by stringers and transverse sub-trusses and topped by a concrete slab. On the parapet wall, there were random stone abutments with cast-iron plaques inscribed with the history of the bridge.

See J Groucott "Brynwern Bridge", Llandrindod Wells, 1977

(Source:- Cadw listed buildings, NJR 25/10/2007)