Dillwyn Colliery

Overview

An anthracite slant colliery at Seven Sisters in the Dulais valley, also called Nant-y-Cafn, opened in 1884 and working the Red Vein. It grew to more than 400 men in the late 1930s and closed in April 1966 after the National Coal Board judged its output atrocious.

History

Dillwyn Colliery, also known as Nant-y-Cafn, was an anthracite slant at Seven Sisters in the Dulais valley. It was opened in 1884, by David Thomas or by John Garbutt and Sons of Crynant, who owned it in 1896, when it employed 60 men with John Garbutt junior as manager. William Thomas and Sons had it in 1900. By 1908 the Dillwyn Colliery Company owned it, with 197 men and John Howells as manager, and in 1923 its upper and lower slants produced 100,000 tons of coal from the Red Vein with 213 men. It was served by the Neath and Brecon Railway.

The Dillwyn Colliery Company went into receivership in August 1928, and a new company of 1929, chaired by Sir David Rees Llewellyn, took it over. Evans and Bevan, who also ran the colliery, opened a new No. 3 slant that greatly increased output, and 430 men worked there in 1938. The colliery had its own washery.

At nationalisation in 1947 the No. 1 and No. 2 slants employed 508 men underground and 85 on the surface. In 1954-55 Dillwyn was one of 42 collieries whose accident rates concerned both the National Coal Board and the miners' union. In early 1966 the Coal Board, citing output per manshift down from 23.6 hundredweight in 1963-64 to 13.1 and losses up to £4.22 a ton, cut the workforce from 446 to 216, moving the rest to Treforgan, and closed the colliery in April 1966.

Geology

The Red Vein anthracite seam.

Workings

Slant mines: the Dillwyn upper and lower slants, later Nos. 1, 2 and 3, with a fan drift and the colliery's own washery.

Closure

Closed by the National Coal Board in April 1966 for poor output and heavy losses; part of the workforce moved to Treforgan.

What remains

Unknown.

Redevelopment

Unknown.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• The anthracite slant was opened in 1884. ¹
• It employed 213 men on the Red Vein in 1923 and 430 in 1938. ¹
• Fatal accidents were recorded at Dillwyn, Seven Sisters, in 1909 and 1910. ²
• The Dillwyn Nos. 1 and 2 workings in the Red Vein were abandoned in 1966. ³
• The National Coal Board closed the colliery in April 1966 after output per manshift fell to 13.1 hundredweight. ¹

Photographs & further reading

Sources

1. (secondary) Welsh Coal Mines: Dillwyn Colliery, Dulais Valley — Welsh Coal Mines
2. (secondary) NMRS coal mining accidents and deaths database — Northern Mine Research Society
3. (primary) BGS / Mining Remediation Authority mine plan: DILLWYN NOS 1 & 2 (Red Vein), abandoned 1966 — British Geological Survey

Record created: 10 October 2026 · Last researched: 10 October 2026