The king involved in the Union of the Crowns in 1603 was James VI (rather than IV) of Scotland and I of England. He did speak and had frequently written in Scots. However, even he himself revised these writings into 'standard' English later. From the 5th century onwards Brythonic or Cumbric Celtic were spoken in Scotland south of the Forth/Clyde line, both of them forms of early Welsh, in effect. Gaelic had come into western Scotland, brought by the Irish, who were actually the original 'Scots'. As the Angles extended their influence northwards from Northumbria, their Germanic dialect replaced Gaelic/Celtic. After the Norman Conquest, many powerful men were granted lands north of the border and so the upper classes spoke Norman French and the rest a form of Northern English, influenced by the Scandinavian of the Vikings. Indeed, 'Scots' as the name of a language as such was never mentioned before the 1490s. Thereafter, the new English Bible was popularised by John Knox himself and the Union of the Crowns meant the Scottish royal court moved to London. These two last-mentioned facts were really the beginning of the end as far as Scots being a national language was concerned. However, neither it NOR Gaelic ever were really the common language of the inhabitants of Scotland.