Throughout 2025, Glandŵr Cymru, the Canal & River Trust in Wales is celebrating the 225th anniversary of the Brecon Canal.

The Monmouthshire & Brecon Canal started as two separate waterways - the Monmouthshire Canal and the Brecknock & Abergavenny Canal. Although they were joined at Pontymoile in 1812, this year’s anniversary marks the northern Brecon Canal’s completion, when coal first reached Brecon Basin on Christmas Eve 1800.”

David Viner, heritage consultant at Canal & River Trust, is telling the story of the canal. The challenge of Pencelli Castle and the influence of the railways on the canal feature in David’s next look back.

Two miles from Talybont, Thomas Dadford encountered another obstacle to his canal line - the substantial mound of Pencelli Castle. Originally a Norman motte and bailey fortification, this had grown into a substantial castle by the 1300s. The remains have long since disappeared, but the canal still follows the course of the moat looping around a steeply wooded hillside. An accommodation bridge at its foot, included for estate workers to cross the canal, was appropriately named Castle Bridge.

Alongside is a feature added 80 years later as canal trade gave way to railway traffic. The diamond-shaped iron weight restriction sign is evidence of the canal’s ownership by the Great Western Railway Company after 1880. About the same time steam driven traction engines were coming into use for operating agricultural machinery. These giants travelled around between farms and the new owners were very concerned that smaller canal bridges built for horse and carts could not withstand the massive extra loading on them. A pair of weight signs mounted on lengths of former railway lines were raised at every bridge, with removable plates indicating the maximum weight for each location. Many remain today, as much part of the canal’s heritage as the original masonry bridges.