St David's Colliery explosion, 1840

Late in June 1840 firedamp exploded underground at St David's Colliery near Llanelli, burning twenty-six men and boys. Five were killed, among them a boy of ten, and a sixth, David Samuel, fourteen, died of his injuries on 15 July. Survivors escaped only by retreating at once from the part of the mine where the gas fired. A newspaper said no one was to blame.

Date	27 June 1840
Mine	St David's Colliery
Region	Carmarthenshire
Type	Explosion
Fatalities	6 (Henry Lewis, 17; William Williams, 20; Thomas John, 10; William Hugh, 25; Griffith Morgan, 14; and David Samuel, 14, who died on 15 July. Welsh Coal Mines describes the immediate dead as three boys and two men; the contemporary Gazette said two boys and two men.)
Injuries	Twenty-six burned in all; the Gazette said many of those who escaped were so badly injured their lives were in danger.
Context	During active mining (The Llangennech company's St David's Colliery between Bryn and Dafen near Llanelli, eight years after its shaft became the deepest in the South Wales coalfield.)

Location

Plotted at St David's Colliery. Recorded location. The large pin is the mine; the small round markers are the nearest mines on record. Click one for its page. View on full map

Cause

An explosion of firedamp underground; how it was ignited is not recorded.

What happened

The Gazette reported a violent explosion of fire damp in which ten to twenty colliers escaped the same fate as the dead only by immediately retreating from the part of the mine where the ignition occurred. The Cambrian of Saturday 4 July 1840 also reported the explosion as 'on Saturday last', that is 27 June, so the 6 July in the Durham Mining Museum's list cannot be the date of the explosion.

Investigation & inquiry

The Gazette and The Cambrian both reported that no blame could be attached to any party.

Memorials & commemoration

The explosion is remembered as the 1840 Llangennech Colliery disaster on a plaque at the Welsh National Mining Memorial Garden at Senghenydd.

What's uncertain

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

Welsh Coal Mines dates the explosion 27 June 1840, and the Glamorgan, Monmouth and Brecon Gazette of Saturday 11 July 1840 reports it as 'on Saturday week'. (disputed) ¹
The Durham Mining Museum lists the explosion under July 1840 and gives 6 July 1840 as the date of death of five of the dead, David Samuel dying on 15 July. (disputed) ²

Recorded claims

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

There was an explosion at the mine on 27 June 1840, when twenty-six men were burned and three boys and two men killed: Henry Lewis (17), William Williams (20), Thomas John (10), William Hugh (25), Griffith Morgan (14) and David Samuel (14), who died on 15 July of his injuries. ^1,2
Welsh Coal Mines dates the explosion 27 June 1840, and the Glamorgan, Monmouth and Brecon Gazette of Saturday 11 July 1840 reports it as 'on Saturday week'. (disputed) ¹
The Durham Mining Museum lists the explosion under July 1840 and gives 6 July 1840 as the date of death of five of the dead, David Samuel dying on 15 July. (disputed) ²
The Gazette reported the immediate death of two boys and two men, ten to twenty others escaping only by immediate retreat, many so badly injured their lives were in danger, and that no blame could be attributed to anyone. ¹
The Cambrian of 4 July 1840 reported a violent explosion of firedamp at St David's Colliery near Llanelly 'on Saturday last', which killed two boys and two men outright. ^3,4
The explosion is commemorated as the 1840 Llangennech Colliery disaster on a plaque at the Welsh National and Universal Mining Memorial Garden, Senghenydd. ⁵

Related terminology

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

Colliery (contextual relationship)
Named in this record’s summary: “Late in June 1840 firedamp exploded underground at St David's Colliery near Llanelli, burning twenty-six men and boys. Five were killed,…”
Firedamp (direct cause)
Firedamp exploded underground.

Sources

(secondary) St. David's Colliery — Welsh Coal Mines
(primary) St. David's Colliery — Durham Mining Museum
(primary) Fatal colliery explosion (The Cambrian, 4 July 1840) — Durham Mining Museum
(primary) Swansea news column (St David's Colliery explosion), 4 July 1840 — The Cambrian (Welsh Newspapers Online, National Library of Wales)
(primary) 1840 Llangennech Colliery disaster (memorial) — Durham Mining Museum

Record created: 11 September 2026 · Last researched: 3 November 2026