When James VI of Scotland and I of England proclaimed himself King of Great Britain he proposed a merger of parliaments as he had joined two crowns in his own person ascending the throne of England in 1603. For James, the Cambro-Celtic past led to an Anglo-Scottish present, and Wales stood as the ideal.　Although the parliamentary union of Great Britain was not initiated for another 100 years, Parliament’s denial failed to deter James from wanting a Great Britain, and R. A.’s play The Valiant Welshman became part of the public spectacle of unity required to nurture James’s dream. The Valiant Welshman, the Scottish James, and the Formation of Great Britain　considers national, regional and linguistic identity and explores how R.A.’s play promotes Wales, serves King James and reveals what it means to be Welsh and Scots in a newly forming "Great Britain."