I think it was Scotland who "expanded" into England in 1603 when King James the VI of Scotland became King James I of England!
Both countries have had kings for over a thousand years!
Scotland since 843!
From WiKi;- The monarch of Scotland was the head of state of the Kingdom of Scotland. According to tradition, the first King of Scots was Kenneth I MacAlpin (Cináed mac Ailpín), who founded the state in 843