Clan chief, landowner and eccentric. Known as Francis Mor, Macnab was an exceptional man, standing six feet three inches (1.9m) in height. He inherited the Chieftainship in 1778, together with large debts, many of which were the result of lengthy and unsuccessful litigation by his forebears. Immortalised as 'The Macnab' in the celebrated and striking painting of 1802 by Sir Henry Raeburn (1756 - 1823), Macnab lived his life as the archetypal feudal chieftain and was also a noted eccentric. He had a dislike of the government involving itself in what he regarded as his affairs and this included a particular hatred of excisemen in search the illegal whisky produced by his clansmen.
The dramatic magnificence of Raeburn's painting, which is now on permanent loan to Kelvingrove Art Gallery & Museum (Glasgow), and of The Macnab's depiction, hid the poverty in which he lived, exacerbated by his own extravagance and a liking for drinking, gambling and womanising. His debts brought the necessity to mortgage much of his property and when he died, unmarried, at Callander, he was reputed to owe the enormous sum of £35,000. Thereafter his nephew and heir, Archibald Macnab (1777 - 1860), sold the clan lands to pay off the debts and emigrated for Canada.