In 1829 depression set in in the iron industry which was to last for three years. As a result Merthyr Tydfil Ironmasters made many workers redundant and cut the wages of those in work. Against a background of rising prices this caused severe hardship for many of the working people of the area and, in order to survive, many people were forced into debt. Often they were unable to pay off their debts and their creditirs would then turn to the Court of Requests which had been set up in 1809 to allow the bailiffs to seize the property of debtors. As a result the Court was hated by many people who saw it as the reason for their losing their property.

Against this background the Radicals of Merthyr, as part of the National movement for political reform, organised themselves into a Political Union in 1830 to lead the local campaign for reform. In November 1830 they called for demonstrations in Merthyr to protest against the Truck System and the Corn Laws. The campaign was actually supported by some local Ironmasters. William Crawshay of Cyfarthfa Ironworks and Josiah John Guest of Dowlais Ironworks, for example, both supported the campaign. By the end of the year 1830 the campaign had broadened to embrace the Reform of Parliament, and the election of a Liberal Government in Great Britain led to a bill being brought before Parliament to reform the House of Commons. The Bill was welcomed by the Merthyr Radicals as a step in the right direction, although it did not give Merthyr a Parliamentary Constituency and only extended the right to vote to the Middle Classes rather than the workers. In April 1831, however, the Bill was defeated in a House of Commons vote, the Government resigned and a new General Election was called to fight on the issue of Parliamentary Reform.

In May 1831 a huge demonstration in favour of Reform was held at Merthyr Tydfil. William Crawshay, the Ironmaster, who supported Reform, describing the demonstration, reported that a local shopkeeper, Mr. Stephens, would not support Reform and around 5000 demonstrators massed outside his house and threatened to hang him and threw stones and other missiles at his windows. Thomas Llewellin and another of the ringleaders, were arrested the next day, but a mob of around 3000 threatened to rescue them, burn down Mr Stephens' house and murder him. As a result Mr Stephens dropped charges against them and they were released. (William Crawshay: The Late Riots at Merthyr Tydfil, 1831).

Despite Crawshay's support for the Reforms he was forced , in March 1831, to announce cuts in the wages of his workers and redundancies. In May the wage cuts took effect and he made 84 of his puddlers redundant. It was this, combined with similar situations in other ironworks, the hatred of the activities of the Court of Requests, and some stirring up by political agitators which led to the Merthyr Rising. On 30 May 1831 at the Waun Common above Dowlais a mass meeting of over 2000 workers from Merthyr & Monmouthshire discussed :-

Petitioning the King for Reform

the abolition of the Court of Requests

the state of wages in the iron industry

One person, a stranger, advocated strike action. This stranger was probably a representative of the National Association of the Protection of Labour, a trade union which had been formed in the North of England in 1830, and which had already set up Colliers Union branches in North Wales and was attempting to do so in South Wales.

Matters came to a head on 31 May 1831.  Bailiffs from the Court of Requests arrived at the home of Lewis Lewis, known as Lewis the Huntsman, who was born at Pyle but was now residing at Penderyn near Merthyr.  Lewis, with the support of neighbours, managed to stop them spiriting away his property.  However by means of compromise the local Magistrate allowed the bailiffs to take a trunk belonging to Lewis.  Refusing to accept this, Lewis and a crowd of followers seized the trunk back from a shopkeeper who was now in possession of it.  The Merthyr Rising had begun.

Lewis' growing army marched on to Merthyr where they demanded back any goods which had been removed by the Court of Requests and returned them to their rightful owners.   Lewis was a moral man and carried out this redistribution fairly.  For example, in one instance regarding the seizing of a chest of drawers from a poor woman who had bought it legitimately from a debtor's court, Lewis made sure she had her money back before returning it to the original owner.

Local Magistrates were quick to realise that swift action had to be taken to restore order.  There was no Police Force in 1831 - the Glamorgan Constabulary would not exist for another 10 years, so Special Constables were quickly sworn in from local tradespeople in an effort to keep the peace.  Following an attack on the home of the President of the Court of Requests, Joseph Coffin, it was inevitable that the soldiers would have to be brought it to quell this serious disturbance.  The Royal Glamorgan Light Infantry from Cardiff and the Highlanders from Brecon were dispatched to Merthyr.

On the morning of Friday 3 June 1831, the soldiers and an angry crowd of 2,000 confronted each other outside the Castle Inn in Merthyr.

The crowd attacked the soldiers, who eventually seeing their comrades falling began to fire and killed at least 16 people (this would have been a deliberately low estimate).  

Gradually the authorities came to gain the upper hand and arrested Lewis Lewis and a man called Richard Lewis (Dic Penderyn), for allegedly stabbing a soldier called Donald Black, a private from the Highlanders, with a bayonet attached to a gun outside the Castle Inn on 3 June 1831.  Although Black did not identify either Lewis Lewis or Richard Lewis, both were sentenced to death.

Lewis Lewis eventually had his sentence reprieved to transportation for life.   This was in large thanks to the testimony of a Special Constable, John Thomas.   John Thomas owed his life to Lewis Lewis on account of  Lewis throwing himself on top of  a cornered Thomas to protect him from the blows of the rioters. However despite petitions for mercy and the intervention of Joseph Tregelles Price, a Quaker Ironmaster from Neath, who even persuaded the trial judge that Richard Lewis was innocent, Dic Penderyn was hung on the gallows in St. Mary's Street, Cardiff on Saturday 13 August 1831.  The name Dic Penderyn, scapegoat for the Merthyr Rising, has lived on in Welsh hearts ever since.  However, despite Dic Penderyn's mythical appeal, we know very little about him.

The rising at Merthyr cause great alarm to the British Government, who feared that the Colliers Union was behind it. The setting up of lodges of the Union at Merthyr immediately afterward seemed to support this view. Events at Merthyr were used both by opponents of Reform and by its supporters to further their aims. What was seen as most important was that swift, strong action must be taken against the ringleaders.

The trials began on 13 July 1831 at Cardiff Assizes. 28 men and women were tried, 23 of them ironworkers (12 colliers , 2 women, 2 shoemakers and one blacksmith). John Phelps, David Hughes, Thomas Vaughan and David Thomas were all found guilty of attacks on the houses of Thomas Wiliams and/or Thomas Lewis. Phelps was sentenced to transportation for 14 years, the others were sentenced to death (but with a recommendation for transportation for life instead). Lewis Lewis and Richard Lewis (Dic Penderyn) were charged with attempting to murder a soldier, Donald Black of the 93rd Highland Regiment, by stabbing him in the leg with a bayonet attached to a gun, outside the Castle Inn on 3rd June. The main evidence against the two Lewis' was from Black himself (though Black himself apparently could not identify his assailant), James Abbott, a hairdresser and Special Constable and James Drew, also a hairdresser and Special Constable. On the slender evidence it was adjudged that Richard Lewis (Dic Penderyn) was guilty but that Lewis Lewis was not guilty ( though he was already under sentence of death for attack on Thomas Lewis' house). Dic Penderyn was sentenced to death. Joseph Tregelles Price, A quaker Ironmaster from Neath, took up the case of Dic Penderyn and Lewis Lewis and presented a petition to have them transported. Evidence was produced that Abbott had threatened Penderyn prior to the 3rd June and people saidthat Penderyn was not there when Black was attacked and that they knew who had carried out the attack but it was not Dic Penderyn. Strangely Lord Melbourne, the Home Secretary, reprieved Lewis Lewis, who was certainly one of those most responsible for the riots, and transported him to Australia, but would not reprieve Penderyn, who was  much less involved in The Rising than some sources would have us believe( indeed one source consulted suggests that he was simply a by-stander at the Castle Hotel). Richard Lewis (Dic Penderyn) was taken from his cell at Cardiff Prison on 13 August 1831 to the gallows at St.Mary Street, Cardiff and there he was executed protesting his innocence. His body was transported across the Vale of Glamorgan to be buried at Margam.

In 1874 the Western Mail reported that a man named Ieuan Parker had confessed to a Minister on his death bed in Pennsylvania, USA that he was the man who attacked Donald Black.