Borderline
In 1222 a commission of six representatives from each kingdom attempted to fix the border line, and one proposed by the English commissioners more or less equates to that which is shown on Ordnance Survey maps today. The western Anglo-Scottish Border was more formally agreed in Edward II's reign with David II of Scotland in 1330, to run along the course of the Esk and Liddel from Gretna to Kershopefoot to delineate between the English and Scottish West Marches. In practice, however, this region was controlled by Wardens of the marches who usually held the land in their own right and met at designated sites, such as the Lochmaben Stone to discuss and settle disputes.
In Scotland the Maxwells, Johnstons and Scotts secured the Scottish West March to Gretna and Langholm, and in England the region was controlled from Carlisle. The Esk basin at Arthuret was a marshy bogland which was difficult to police, with the Scottish jurisdiction having difficulty policing their side from Gretna to Canonbie. The Debatable Land arose because the Graemes, Armstrongs, Elliots and Bells were too powerful, and the Wardens largely left them alone. These four families raided equally in both England and Scotland, claiming allegiance to neither country; it actually suited both Governments to have such a "buffer" zone, so the district became a sort of no-mans land, where neither country could or would enforce their jurisdiction.
Eventually the general lawlessness spilled over and both Wardens demanded that the Debateable Land be eradicated. So in 1552 the French ambassador was appointed to finalise the Border line, together with Lord Wharton (of the Battle of Solway Moss fame) and Sir Thomas Chaloner nominated and appointed from England; Sir James Douglas of Drumlanrig and Richard Maitland of Lethington likewise nominated and appointed from Scotland. The Commissioners agreed to a compromise demarcation line suggested by the French Ambassador, and issued a final declaration that the borderline would run from the Sark to a point on Esk, opposite the house of Fergus Greme; a cross pattee at each end and styled 'this is the least and fynal lyne of the particion concluded xxiiij Septembris 1552.'
Read more about this topic: Scots' Dike, Debatable Lands