The firm said Ransford would be based in London but would make regular trips to Lagos, Nigeria.
Africa is a core component of Actis’ business, with about $1.5bn invested across the continent.
The firm’s Africa co-head, John van Wyk, said: “Actis has always led the way in Africa.
“Our insight into consumer trends and investment opportunities on the continent is unmatched.
“With his deep understanding of private equity and his prior experience in West Africa, Mark is a welcome addition to the team.”
Ransford said, “I believe demographic trends drive equity returns.
“This makes me pretty excited about identifying investment opportunities in West Africa and specifically in Nigeria, the most populous country on the continent.
“I look forward to working with my new colleagues in Lagos and Africa, drawing on their pan-emerging markets experience.”
Actis’ current Nigeria investments include the Diamond Bank, oil and gas production company Seven Energy, foam products manufacturer Mouka and real estate developments Ikeja City Mall and Heritage Place.
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