Ystalyfera Colliery derailment, 1947

In July 1947 two riders at Ystalyfera Colliery in the upper Swansea Valley, William Thomas and William Edwards, were killed when the two-tram journey taking them up a slant to look into a signalling fault came off the rails.

Cause

A spake of two trams, used in an emergency to take men to the surface, was derailed on the slant.

What happened

That night there had been a delay in taking the men down the slant because of trouble with the signalling. At the bottom, Thomas suggested that he and Edwards go back up by the other slant and examine the signalling on both, and the overman, William David Ware, agreed. Shortly afterwards Ware was called to that slant and found Edwards semi-conscious and being attended to, and fifteen or twenty yards away two derailed drams, with Thomas dead in the foremost.

Investigation & inquiry

At the inquest the coroner asked Ware whether he had any theory of how the trams had left the rails; he said he had no explanation. Dr David Stewart said Thomas had died instantly of a fractured skull and Edwards in Swansea Hospital from shock caused by multiple injuries.

What's uncertain

Points where sources disagree or the record could not be settled; both accounts are kept. All open questions in the archive.

• The accident happened on 4 July 1947. (disputed) ¹
• The accident happened on 6 July 1947. (disputed) ^2,3

Recorded claims

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

• In July 1947 two men, William Thomas and William Edwards, were killed when a journey of two trams came off the rails on a slant at Ystalyfera Colliery. ^1,2,3
• The accident happened on 4 July 1947. (disputed) ¹
• The accident happened on 6 July 1947. (disputed) ^2,3
• The two trams were being used in an emergency to take men to the surface when they were derailed. ^2,3
• Thomas died instantly of a fractured skull; Edwards died in Swansea Hospital of shock from multiple injuries. ¹

Related terminology

Mining terms this disaster is structurally linked to, with the nature of the relationship.

• Fault (contextual relationship)
  Named twice in this record, first in the summary: “…two-tram journey taking them up a slant to look into a signalling fault came off the rails.”
• Journey (contextual relationship)
  Named in this record’s summary: “…William Thomas and William Edwards, were killed when the two-tram journey taking them up a slant to look into a signalling fault came off the…”
• Overman (contextual relationship)
  Named in this record’s narrative: “…up by the other slant and examine the signalling on both, and the overman, William David Ware, agreed. Shortly afterwards Ware was called to…”
• Slant (contextual relationship)
  Named 5 times in this record, first in the summary: “…Edwards, were killed when the two-tram journey taking them up a slant to look into a signalling fault came off the rails.”
• Tub (contextual relationship)
  Named 3 times in this record, first in the cause: “A spake of two trams, used in an emergency to take men to the surface, was derailed on…”

Sources

1. (secondary) 1947 (Welsh mining fatalities by date) — Welsh Coal Mines
2. (secondary) NMRS Coal Mining Accidents and Deaths: William Thomas, Ystalyfera, 6 July 1947 — Northern Mine Research Society
3. (secondary) NMRS Coal Mining Accidents and Deaths: William Edwards, Ystalyfera, 6 July 1947 — Northern Mine Research Society

Record created: 25 October 2026 · Last researched: 25 October 2026