Along the eastern shoreline of Africa, as in the Red Sea and the Persian Gulf, William Mackinnon, BI and Gray Dawes & Co spent much of the 1870s in trade-promoting activities – running steamships to a regular timetable, setting-up local agencies, attempting to develop interior lines of communication, and trying to secure British consular support for these pursuits. However, these African margins of BI's ‘Arabian’ system possessed their own distinguishing characteristics. In particular, the group's operations on eastern African shores acquired a philanthropic or humanitarian dimension – in which goals of opening up the foreign trade of less developed regions, and incorporating them more fully into the expanding nineteenth century international economy, became overlaid with the additional objectives embodied in the mid-Victorian concept of ‘Commerce and Christianity’. At the African end of the ‘Arabian’ steamship network a Christian evangelisation movement, linked to popular anti-slave trade sentiment, was at work in a way that could not be found in the Muslim countries of the Gulf and the Red Sea. Thanks largely to the legacy of David Livingstone, these forces became intertwined with the development of trade and transport in eastern Africa, and with the harnessing of steampower to break down the barriers of geographic distance. Consequently, in penetrating Africa from Asia, William Mackinnon and his firms moved into an environment that was distinctive in British imperial terms as well as in specifically local political and economic conditions. In doing so they acquired an ambiguity about their motives and purpose. To the patriotism with profits that characterised their operations in the Persian Gulf an additional element of philanthropy now came to be attached.

The key to these differences was the way that William Mackinnon hitched himself and his firms to the pro-consular career of Sir Henry Bartle Frere. Frere was a brilliant self-promoter and publicist, and a good public orator, who moved easily within British government circles and influenced much of their Indian and imperial policy. He thought and wrote in terms of grand designs of imperial expansion, and of the geo-strategic significance of railway and steamship routes in linking together the various British-ruled territories.