Original sentence: In the far north, Viking incursions brought Norse speakers into Caithness, Orkney and Shetland.Speakers of Northumbrian Old English settled in south eastern Scotland in the 7th century, at which time Celtic Brythonic was spoken in the south of Scotland to a little way north of the Firth of Forth and the Firth of Clyde, and Pictish was spoken further north: almost nothing is known nowadays about Pictish
Edited sentence: Speakers of Northumbrian Old English settled in south eastern Scotland in the 7th century, at which time Scotland was mostly Celtic-speaking, with Brythonic in the south to a little way north of the Firth of Forth and the Firth of Clyde, and Pictish further north: almost nothing is known nowadays about Pictish