Balfour (1848-1930) an amateur philosopher without great academic distinction, had the easiest rise to the premiership since the 18th century, his career being sponsored by his uncle Salisbury. (His lifetime total of 27 years’ service in the Cabinet is not the most of any British statesman, being exceeded by Newcastle (c. 38 years) and John Fane, 10th Earl of Westmorland (1759-1841, c. 33 years), possibly among others.)1 His premiership deserves to be remembered for two things. One was the attempt by Joseph Chamberlain to reverse 60 years of unilateral free trade, which Balfour did much to thwart. The second was the reversal of a century of British foreign policy by forming the Entente Cordiale with France, thus facilitating the division of Europe into two mutually hostile armed camps that was to prove fatal to global peace a decade later.
Despite a reforming Education Act, Army modernisation, and another Irish Land Act that further weakened property rights, Balfour’s tenure of office led to the worst Conservative party election result ever. He also hated the Conservative rank and file, which his uncle hadn’t. Balfour should rank near the bottom, being is the first of several 20th century prime ministers who did more harm than good, and should thus rank below, not above, the short-term nonentities.
 Leonard, op. cit., makes this claim for Balfour, but is wrong.