Simplify the following text for a Grade 5 native English-speaking person.
Original: On 24 March 1603 , he also became King of England and Ireland as James I when he inherited the English and Irish crowns and thereby united the Crown of the Kingdom of Scotland , with the crowns of the Kingdoms of England and Ireland ( each country remained legally separate , with their own Parliaments , judiciary , coinage etc. , though each were ruled by James ) . James VI & I continued to hold all three crowns until his death in 1625 , but based himself in England ( the larger of the three realms ) from 1603 .
Simplified: He ruled in England and Ireland from 24 March 1603 until his death .