British antislavery pressure helped force the 1877 convention. [fact]
The farther south Ismaïl moved, therefore, the more vigilant the influ- ential members of the Anti-Slavery Society became. Not only did they peti- tion the khedive directly to abolish the slave trade, but they also had the ear of many individuals in Parliament and the Foreign Office. So loud were their voices that, by 1877, Ismaïl signed the Anglo-Egyptian Slave Trade Convention.
Eve M. Troutt Powell, A Different Shade of Coloni…, loc. 295