Casting the British Empire as a force against Slavery in the 1770s seems to be an overly generous assessment. The abolition movement was confined to a tiny fringe of activists until well after the revolution was under way, with the first organised abolition group starting in 1785.
In addition, abolition in the British colonies was a slow, drawn-out affair, that catered excessively to the needs of the plantation aristocracy who held huge clout in Parliament, and who were able to wring huge compensation for the loss of their “property” from the state.
Even then, WEB DuBois was critical of the extent of influence that abolitionism had in the end of slavery in British colonies, arguing that the shift by the British government to an anti-slavery position was driven mainly by economic factors, which would not have been in place had Britain kept its American colonies.
The rise of liberal and philanthropic thought in the latter part of the eighteenth century accounts, of course, for no little of the growth of opposition to slavery and the slave trade; but it accounts for only a part of it. Other and dominant factors were the diminishing returns of the African slave trade itself, the bankruptcy of the West Indian sugar economy through the Haitian revolution, the interference of Napoleon and the competition of Spain. Without this pressure of economic forces, Parliament would not have yielded so easily to the abolition crusade. Moreover, new fields of investment and profit were being opened to Englishmen by the consolidation of the empire in India and by the acquisition of new spheres of influence in China and elsewhere. In Africa, British rule was actually strengthened by the anti-slavery crusade, for new territory was annexed and controlled under the aegis of emancipation. It would not be right to question for a moment the sincerity of Sharpe, Wilberforce, Buxton and their followers. But the moral force they represented would have met with greater resistance had it not been working along lines favorable to English investment and colonial profit