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 finalized in 1237 by the Treaty of York.