The chapter-house, adjoining the choir, was built by Bishop Thomas Lauder (1395-1481) in 1469, and the vault beneath is the burial-place of the Atholl Murrays.
Lauder also began the tower, completed in 1501.
In the Scottish campaign of 1547 he was present at the barren victory of Pinkie, and in the next year was taken prisoner at Saint Monance, but aided by his persuasive tongue he escaped to the English garrison at Lauder, where he was once more besieged, only returning to England on the conclusion of peace in 1550.
Archibald Douglas, earl of Angus, opened the door and seized Mar, who was forthwith dragged to Lauder Bridge and there, along with six other obnoxious favourites, hanged in sight of his royal master.
The duke of Gloucester (later Richard III.) marched north and took Berwick, while the earl of Angus, with other nobles, hanged Cochrane and other favourites of James over Lauder bridge.