British governing classes then, forgoing after 1850 opposition to the advance of American power, found themselves involved again, as before 1832, in the problem of the possible influence of a prosperous American democracy upon an unenfranchised public opinion at home. Also, for all Englishmen, of whatever class, in spite of rivalry in power, of opposing theories of trade, of divergent political institutions, there existed a vague, though influential, pride in the advance of a people of similar race, sprung from British loins. And there remained for all Englishmen also one puzzling and discreditable American institution, slavery—held up to scorn by the critics of the United States, difficult of excuse among her friends.
Agitation conducted by the great philanthropist, Wilberforce, had early committed British Government and people to a crusade against the African slave trade. This British policy was clearly announced to the world in the negotiations at Vienna in 1814-15. But Britain herself still supported the institution of slavery in her West Indian colonies and it was not until British humanitarian sentiment had forced emancipation upon the unwilling sugar planters, in 1833, that the nation was morally free to criticize American domestic slavery. Meanwhile great emancipation societies, with many branches, all virile and active, had grown up in England and in Scotland. These now turned to an attack on slavery the world over, and especially on American slavery. The great American abolitionist, Garrison, found more support in England than in his own country; his weekly paper, The Liberator, is full of messages of cheer from British friends and societies, and of quotations from a sympathetic, though generally provincial, British press.
From 1830 to 1850 British anti-slavery sentiment was at its height. It watched with anxiety the evidence of a developing struggle over slavery in the United States, hopeful, as each crisis arose, that the free Northern States would impose their will upon the Southern Slave States. But as each crisis turned to compromise, seemingly enhancing the power of the South, and committing America to a retention of slavery, the hopes of British abolitionists waned. The North did indeed, to British opinion, become identified with opposition to the expansion of slavery, but after the “great compromise of 1850,” where the elder American statesmen of both North and South proclaimed the “finality” of that measure, British sympathy for the North rapidly lessened. Moreover, after 1850, there was in Britain itself a decay of general humanitarian sentiment as regards slavery. The crusade had begun to seem hopeless and the earlier vigorous agitators were dead. The British Government still maintained its naval squadron for the suppression of the African slave trade, but the British official mind no longer keenly interested itself either in this effort or in the general question of slavery.