Campbell-Bannerman (1836-1908) came from a wealthy Scottish commercial family, and served in the Commons from 1868, becoming War Secretary in the Liberal governments of 1886 and 1892-95, before an unsuccessful attempt at the Speakership in 1895. At the end of 1898, after Harcourt had resigned and Asquith had declined, Campbell-Bannerman became leader of the Liberal party, which he held through the defeat of 1900, becoming prime minister at the end of 1905.
Campbell-Bannerman took office at the head of a Liberal Party that had split during the Boer War and was divided between the “Imperialists” who wanted greater military spending and to deepen the French alliance and Radical semi-pacifists. He was also to be hampered by a House of Lords that was heavily Tory, limiting his ability to pass major legislation. Nevertheless, having excellent people skills he negotiated a pact with the emerging Labour Party and won a massive election victory in 1906.
During his 28 months in office Campbell-Bannerman passed a Trades Disputes Act broadening trades unions legal immunities, but the Education Bill was blocked by the House of Lords. He also agreed a settlement with South Africa, which reconciled the Boers at the long-term cost of not providing for even a limited African franchise. Campbell-Bannerman prepared the way for the major social legislation of the Asquith years -- the Old Age Pensions provision was passed in the 1908 Budget just after his death. However, he allowed the Entente Cordiale to be deepened into a Triple Alliance with Russia, increasing the likelihood of European war. He maintained good relations with the Labour Party and mildly favoured women’s suffrage, two issues that would trouble his successors.
The Victorian quiescence was over by Campbell-Bannerman’s time, and he should get credit for navigating a steady path in difficult circumstances, while the Russian alliance, the one major negative of his term, was negotiated by his more belligerent colleagues. He should rank in the low 20s, just above average.