The debate about whether the Industrial Revolution was a good or a bad thing for the Welsh language will probably last as long as Welsh itself.

Modern industry started in the 18th century, and its growth accelerated throughout the 19th as production switched from metal to coal mining. By the early 20th century, about one out of every four Welsh workers was a coal miner.

Initially, the majority of the workers were Welsh. They migrated to the Valleys from west, mid and north Wales and the everyday language among the workers at the furnaces and coal mines would have been Welsh. There were English speaking migrants, but relatively few. As many of their fellow workers were monoglot Welsh, they tended to learn the language.

As the 19th century progressed, the rate of immigration from outside Wales increased. Most of the new arrivals came from England; if they did learn the native language, it was for practical reasons or out of good will and a desire to integrate. There was certainly no formal requirement, a state of affairs which can be traced back to the infamous Language Clause of the Act of Union of 1536. English was still the only official language in Wales.

Other anglicising influences came with the spread of the railways and the rise of daily newspapers. There were Welsh language magazines which carried news, but they were available only in monthly or weekly editions. Trains delivering London daily papers made it possible for a worker in the Valleys to find out the latest news from the British Empire as long as he, or she, could read English.

In the heat of industrial change, English was seen as the language of progress. Communities in the Valley were at the forefront of industrial and social change, not only in Wales but internationally. Welsh began to lag behind English as an effective language in this new world.

During the 20 years leading up to the First World War immigrants poured into the coal mining areas at a rate second only to America. This last tide of immigrants tipped the language balance of many communities in south Wales. A philosophy called Socialism emerged which sought to unite the immigrants and the native workers in the name of class to pursue political power. This movement was largely indifferent to the fortunes of the Welsh language.

When the 1911 census showed that for the first time for around 2,000 years Welsh was a minority language, spoken by just 43.5% of the population, the news caused hardly a ripple.