Alexander Nisbet in A System of Heraldry Vol 1, 1722, states that 'Buchannan of Lenie' is now the representor of 'Buchannan of that Ilk.' William Buchanan of Auchmar in his history of the clan, published in 1723, details a case that all cadet lines, except one, from George 15th of Buchanan to John Buchanan 19th of Buchanan had expired and on the death of the latter, the chiefship devolved to the cadet line most recently separated from the chiefly line, Buchanan of Auchmar, thus he, William Buchanan of Auchmar, is the chief of Clan Buchanan and that Nisbet is wrong in asserting that Buchanan of Leny is representer of the chiefly line. In Nisbet's (posthumously published) A System of Heraldry Vol 2, 1742, he recognises Buchanan of Auchmar as the successor of the chiefly line. In the 1826 claim for the chiefship by Dr Francis Buchanan-Hamilton, the extinction of both the main chiefly line and the Auchmar line are identified as preconditions to the claim. The later Clan historian, John Guthrie Smith, omits any reference to Buchanan of Auchmar's claim when he details the Buchanans of Auchmar.