Simplify the following text for a Grade 7 native English-speaking person.
Original: Its county town , after which it is named , had been Berwick-upon-Tweed , but the royal burgh changed hands in 1482 , subsequently becoming part of the county of Northumberland , in England .
Simplified: Berwickshire 's first county town was the Royal Burgh of Berwick-upon-Tweed . In 1482 England seized Berwick .