Norman invasion of Wales and Wales in the Late Middle Ages The southern and eastern parts of Great Britain lost to English settlement became known in Welsh as Lloegyr Modern Welsh Lloegr , which may have referred to the kingdom of Mercia originally and which came to refer to England as a whole. His sons, in turn, would found three principal dynasties Aberffraw for Gwynedd, Dinefwr for Deheubarth and Mathrafal for Powys.
Rhodri's grandson Hywel Dda r. Maredudd's great-grandson through his daughter Princess Angharad Gruffydd ap Llywelyn r. Historian John Davies states that Gruffydd was "the only Welsh king ever to rule over the entire territory of Wales Thus, from about until his death in , the whole of Wales recognised the kingship of Gruffydd ap Llywelyn. For about seven brief years, Wales was one, under one ruler, a feat with neither precedent nor successor.
The frontier region, and any English-held lordships in Wales, became known as Marchia Wallie, the Welsh Marches , in which the Marcher Lords were subject to neither English nor Welsh law. With Llywelyn's death and his brother prince Dafydd 's execution, the few remaining Welsh lords did homage for their lands to Edward I.
The king ruled directly in two areas: The existing royal lordships of Montgomery and Builth remained unchanged,  and the remainder of Wales was still controlled by the marcher lords. Caernarfon Castle , birthplace of Edward II of England To help maintain his dominance, Edward constructed a series of great stone castles: Beaumaris , Caernarfon and Conwy.
But the rebellion failed, and Owain went into hiding in ; peace was essentially restored in Wales by The last remnants of Celtic-tradition Welsh law were abolished and replaced by English law by the Laws in Wales Acts and Industrial Wales Dowlais Ironworks by George Childs — Penrhyn Slate Quarries, Prior to the British Industrial Revolution , which saw a rapid economic expansion between and , there were signs of small-scale industries scattered throughout Wales.
With access to local coal deposits and a harbour that could take advantage of Cornwall's copper mines and the copper deposits being extracted from the largest copper mine in the world at Parys Mountain on Anglesey, Swansea developed into the world's major centre for non-ferrous metal smelting in the 19th century.
The Penrhyn Quarry , opened in by Richard Pennant , was employing 15, men by the late 19th century,  and along with Dinorwic Quarry , it dominated the Welsh slate trade. Although slate quarrying has been described as 'the most Welsh of Welsh industries',  it is coal mining which has become the single industry synonymous with Wales and its people.
Initially, coal seams were exploited to provide energy for local metal industries but, with the opening of canal systems and later the railways, Welsh coal mining saw a boom in its demand. By its height in , Wales was producing almost 61 million tons of coal. As well as in south Wales, there was also a significant coalfield in the north-east of the country, particularly around Wrexham.
Output from the coalfields continued to increase, with the Rhondda Valley recording a peak of 9. A total of , Welshmen served in the war, representing Since , the Liberal Party had held a parliamentary majority in Wales and, following the general election of , only one non-Liberal Member of Parliament, Keir Hardie of Merthyr Tydfil , represented a Welsh constituency at Westminster.