A Zambian businessman lost a London lawsuit against Atlas Mara, the African investment vehicle set up by former Barclays boss Bob Diamond, over the acquisition of a Zambian bank. Rajan Mahtani sued Atlas Mara over the sale of Finance Bank Zambia, alleging he received less than a quarter of the $215 million said to have been offered in 2015. But Judge Christopher Butcher dismissed Mahtani's case in a written ruling on Wednesday, following a trial at London's High Court last year. Mahtani, who founded Finance Bank Zambia in 1986, had accused Atlas Mara of breaching the terms of the takeover…