question: Meirchion Gul was a King of which Brittonic-speaking region of Northern England and Southern Scotland?
answer: Rheged
context: Title: Bonedd Gwŷr y Gogledd
  Passage: Bonedd Gwŷr y Gogledd (English: The Descent of the Men of the North ) is a brief Middle Welsh tract which claims to give the pedigrees of twenty 6th century rulers of the Hen Ogledd, the Brittonic-speaking parts of southern Scotland and northern England.  It is attested in a number of manuscripts, the earliest being NLW, Peniarth MS 45, which has been dated to the late 13th century.  The text may have been composed in the 12th century.  The historicity of much of the information is spurious or in doubt.  Although certain parts are in agreement with the earlier Harleian genealogies, the text represents a substantial revision seeking to integrate the branches of many rulers and heroes who are prominent in other traditions, such as the Rheged prince Llywarch Hen.
  Title: Coel Hen
  Passage: Coel (Old Welsh: "Coil") or Coel Hen ("Coel the Old") is a figure prominent in Welsh literature and legend since the Middle Ages.  Early Welsh tradition knew of a "Coel Hen" (Coel the Old), a "circa" Fourth Century CE leader in Roman or Sub-Roman Britain and the progenitor of several kingly lines in the Hen Ogledd ("the Old North"), the Brittonic-speaking part of northern England and southern Scotland.  Later medieval legend told of a Coel, apparently derived from Coel Hen, who was the father of Saint Helena and the grandfather of Roman Emperor Constantine the Great.  Other similarly named characters may be confused or conflated with the Welsh Coel.  The legendary "King Coel" is sometimes supposed to be the historical basis for the popular nursery rhyme "Old King Cole", but this is unlikely.
  Title: Meirchion Gul
  Passage: Meirchion Gul was probably a late 5th-century king of Rheged, a Brythonic realm in the area of sub-Roman known as the "Hen Ogledd" (in the North of England and Southern Scotland today).
  Title: Rheged
  Passage: Rheged (] ) was one of the kingdoms of the "Hen Ogledd" ("Old North"), the Brittonic-speaking region of what is now Northern England and southern Scotland, during the post-Roman era and Early Middle Ages.  It is recorded in several poetic and bardic sources, although its borders are not described in any of them.  Some modern scholars have suggested that it included what is now Cumbria in North West England and possibly extended into Lancashire and Scotland.  In some sources, Rheged is intimately associated with the king Urien Rheged and his family.  Its inhabitants spoke Cumbric, a Brittonic dialect closely related to Old Welsh.
  Title: Borders Railway
  Passage: The Borders Railway connects the city of Edinburgh with Galashiels and Tweedbank in the Scottish Borders.  The railway follows most of the alignment of the northern part of the Waverley Route, a former double-track line in southern Scotland and northern England that ran between Edinburgh and Carlisle.  That line was controversially closed in 1969, as part of the Beeching cuts, leaving the Borders region without any access to the National Rail network.  Following the closure, a campaign to revive the Waverley Route emerged.  Discussion on reopening the northern part of the line came to a head during the early 2000s.  Following deliberations in the Scottish Parliament, the Waverley Railway (Scotland) Act 2006 received Royal Assent in June 2006.  The project was renamed the "Borders Railway" in August 2008, and building works began in November 2012.  Passenger service on the line began on 6 September 2015, whilst an official opening by Queen Elizabeth II took place on 9 September.
citations: Rheged Meirchion Gul