<P> In 1092, William II led an invasion of Strathclyde, a Celtic kingdom in what is now southwest Scotland and Cumbria . In doing so, he annexed what is now the county of Cumbria to England . In 1124, Henry I ceded what is now southeast Scotland (called Lothian) to the Kingdom of Scotland, in return for the King of Scotland's loyalty . This final cession established what would become the traditional borders of England which have remained largely unchanged since then (except for occasional and temporary changes). This area of land had previously been a part of the Anglian Kingdom of Northumbria . Lothian contained what later became the Scottish capital, Edinburgh . This arrangement was later finalised in 1237 by the Treaty of York . </P> <P> The Duchy of Aquitaine came into personal union with the Kingdom of England upon the accession of Henry II, who had married Eleanor, Duchess of Aquitaine . The Kingdom of England and the Duchy of Normandy remained in personal union until John Lackland, Henry II's son and fifth - generation descendant of William I, lost the continental possessions of the Duchy to Philip II of France in 1204 . A few remnants of Normandy, including the Channel Islands, remained in John's possession, together with most of the Duchy of Aquitaine . </P> <P> Up until the Norman conquest of England, Wales had remained for the most part independent of the Anglo - Saxon kingdoms, although some Welsh kings did sometimes acknowledge the Bretwalda . Soon after the Norman conquest of England, however, some Norman lords began to attack Wales . They conquered and ruled parts of it, acknowledging the overlordship of the Norman kings of England but with considerable local independence . Over many years these "Marcher Lords" conquered more and more of Wales, against considerable resistance led by various Welsh princes, who also often acknowledged the overlordship of the Norman kings of England . </P> <P> Edward I defeated Llywelyn ap Gruffudd, and so effectively conquered Wales, in 1282 . He created the title Prince of Wales for his heir, the future Edward II, in 1301 . Edward I's conquest was brutal and the subsequent repression considerable, as the magnificent Welsh castles such as Conwy, Harlech, and Caernarfon attest; but this event re-united under a single ruler the lands of Roman Britain for the first time since the establishment of the Kingdom of the Jutes in Kent in the 5th century, some 700 years before . Accordingly, this was a highly significant moment in the history of medieval England, as it re-established links with the pre-Saxon past . These links were exploited for political purposes to unite the peoples of the kingdom, including the Anglo - Normans, by popularising Welsh legends . </P>

Who was the first to build a centralized nation in england