At approximately 2.40 p.m. on this day, a loud report was heard above ground at Maerdy Colliery and a column of smoke and dust was seen to issue from the upcast shaft. These signs, were recognisable to everyone familiar with mining at that time as indicating another in the terrible catalogue of disasters that were the dread of everyone working, or living with someone working, underground. Indeed, tragedy had come to the close-knit community of Maerdy with an explosion underground in the 'East Rhondda' district of Maerdy Colliery. The disaster claimed the lives of eighty-one men and boys, sixty-three from suffocation and eighteen from burns and violence.

The Colliery, at that time had only been open for eight years, and belonged to Lockett's Merthyr Steam Coal Company, the local director of which was Mr. William Thomas, the mine manager was Mr. Griffith Thomas, who had been in charge for the previous six years. The coal mined at Maerdy was Steam Coal, a notoriously dry and dusty coal that gives off large quantities of gas. The colliery was regarded, at that time, as one of the best ventilated in South Wales. Using a surface Waddle fan to pump air into the mine and 'blowers' inside the mine to ventilate any areas where build-ups of gas were suspected. Indeed prior to 23rd December 1885 no fatal accident had occurred from an explosion since the Colliery was opened. Underground the mine was divided into two districts, East and West, known locally as the Rhondda and Aberdare. At the time of the explosion, the Colliery employed 961 men, 200 on the night shift and 761 on the day shift. On the 23rd December at 2.40 p.m. there were therefore over 750 men underground. The explosion however was confined to the Eastern or Rhondda District, and those men working the Western or Aberdare District emerged unscathed.

Almost immediately after the explosion was heard teams of rescuers descended the pit, led by Mr. William Thomas and consisting of miners from neighbouring pits, as well as those who had been raised from the unaffected part of Maerdy Colliery itself. Many of the bodies were recovered almost immediately, but because of the difficulties penetrating to the heart of the mine, bodies were still being recovered until the Sunday following the explosion. On the Wednesday afternoon, miraculously, thirty men were recovered unscathed from the mine. Having been working a hundred and twenty yards below the site of the explosion, they had escaped its violence. The funerals for the victims were held at Ferndale and Llanwonno cemeteries, on the Saturday, Sunday and Monday following the disaster amid scenes of great distress and communal mourning.

A Report into the 'Maerdy Colliery Explosion', by A.G.C.Liddell Barrister at Law who had attended the coroners inquest held at the Maerdy Hotel on the 12th to the18th January on behalf of The Secretary of State, was presented to both Houses of Parliament. He states the verdict of the Coroner's Court as being:

The Coal Mines regulations Act, 1872 laid down regulations for when shot firing, for three months after a mine had shown a presence of gas whereby a 'blue cap on the flame of a safety lamp' showed. In these circumstances shot firing should only be undertaken if those underground were evacuated from the area of the mine where the firing was to take place. These rules were to be observed 'where practicable'. Mr. Liddell contends that for reasons of time and trouble these rules were deliberately flouted at Maerdy Colliery, where lamps showing a blue flame were constantly seen in the Colliery. Thus when daily shot firing was undertaken in Maerdy's North Western district, where 122 men were working, only the five men working in the actual heading were withdrawn a distance of fifty yards from where the shot was fired.

Describing the actual explosion itself Mr. Liddell states that the course of the blast from the explosion was approximately one mile long. After reviewing the evidence he goes on to conclude that the explosion originated in an area termed the North west dip, a branch off from the main West heading, He then relates the two theories as to the actual cause of the explosion. Both theories are based around an area where masons were building an archway in a 30-foot high cavity caused by a fall in the roof, the cavity being deemed a danger as a place where gas might accumulate. On the day of the explosion five men were working on this arch on a platform raised about six feet above the roadway, three mason and two assistants. The assistants were allowed to use a naked light of a type known as a 'Comet'. Additionally in the same area, a heading through stone was being driven towards the 4ft. coal seam by blasting with shot. This heading, Mr.Liddell states had only slight deposits of coal dust and had never shown a trace of gas.

Because of these factors Mr. Liddell argues against the first of the two theories that had been proposed for the cause of the explosion namely that:

1) 'That the explosion was caused through the ignition of coal dust in the N.W. dip by the 'comet' lamp used at the arches. That such coal dust was raised by the concussion of a blown out shot in the stone heading'.

2) 'That the explosion was caused by the accumulation of fire damp in the cavity above the arches, and ignited by one of the masons raising the 'comet' lamp into the gas'.

With regards to the first theory, he contends that there was no permission given on the 23rd December for the day shift to fire a shot. Also the one shot hole that had been dug had, according to expert witnesses, never been fired. Additionally the bodies of the four men working on the stone heading at that time were actually found in the heading, whereas if a shot firing had taken place they would have adjourned to a place of safety.

Regarding the second theory, he states it, as being 'the probable cause of the disaster', though he admits that there was enough reasonable doubt to prevent the coroner's jury from accepting it as fact. His support for this theory is based on a number of factors. The nature of the cavity and the space at its top being above the airway constructed for ventilation was, he claims, an ideal place for gas to accumulate. A fireman in the colliery had seen a blue flame, signifying traces of gas, on his safety lamp some three months prior to the explosion, a fact he had not reported in the daily report book. Also on the 31st December, after the explosion, a workmen's examiner found gas filling the cavity down to about six inches above the airway. This was despite extra precautions being taken to dispel gas from the cavity after the explosion. This suggested to Mr. Liddell that the previous precautions would also have been insufficient to dispel gas from building up in the cavity. The direction of the blast, as well as the unlikelihood of gas collecting in any other part of the workings in that area also supported his contention that this is where the initial blast occurred. Although the evidence was not conclusive as to what actually did happen on 23rd December, Mr.Liddell states that even if the explosion did not occur in this manner that. ' There can, I think, be no doubt that it was a dangerous error of judgment to allow the use of the 'Comet'' in the way that it was used. Whatever the actual cause of the initial explosion it was Mr. Liddell's conclusion that the amount of gas involved could not account for the ferocity of the blast that ensued. Thus he believed that however the initial blast occurred, it was the profusion of coal dust in the workings that actually propagated the explosion. Therefore he recommended to the Home Secretary that ' a regular system of watering and removal of dust in coal mines be carried out, and put under a competent officer'. In addition that, 'it would be advisable to prohibit shot firing in dusty parts of a mine without previous watering of all places to which the flame of the shot might extend'.

Early in the January following the explosion the mine was declared safe again, and the surviving miners returned to work in the mine that had so recently claimed the lives of so many of their colleagues.