In 1909 the Bedwas Colliery Company leased 1,475 acres of land, on the slopes of Mynydd y Grug just outside the village of Trethomas.
[1] The purposeful insertion of the word "navigation" was undertaken to entice orders from marine shipping customers, including the Admiralty.
In order to keep the mine profitable, the owners asked the men to take a 20% pay cut in the mid-1920s which led to the banning of the South Wales Miners' Federation (the main Trade Union), following riots.
In the late 1950s NCB approved a major £4 million reorganisation at the colliery, which: electrified the winding; provided a new pit bottom area; an underground loco roadway; a new coal preparation plant was built on the surface.
[3] Following closure in 1985, the colliery was demolished quickly and the shafts filled with rubble, possibly to prevent any chance of it reopening in the future.
The site has since been inherited by Caerphilly County Borough Council, with a majority of the former railway line upgraded to become an extension of the Taff Trail cycle path.
It was proposed that removal of the residual historical remains from the rest of the site would outweigh any economic gain from redevelopment.