Atlas Mara, a new investment company backed by the former boss of Barclays Bob Diamond, said it had raised $325 million by listing on the London Stock Exchange and planned to build a new financial services business in Africa.Diamond embarked upon the venture after he was ousted from Barclays last year when the bank was fined $450 million for alleged manipulation of the Libor interbank lending rate.He and African-focused entrepreneur Ashish Thakkar have invested a combined $20 million in Atlas Mara and said in a prospectus published on Tuesday they saw significant gaps within the African financial services sector, partly because European lenders quit the region after the financial crisis to focus instead on building capital to meet tougher regulations.That presented an opportunity, they said, to make an acquisition that could be developed into a financial institution "to support economic growth and strengthen financial systems in Africa”.The scope for growth in Africa is significant. Barely a quarter of sub-Saharan Africans have a bank account, yet economic growth in the region is set to outpace the global average over the next three years, according to World Bank figures.British banks Barclays and Standard Chartered have both said they expect strong growth from their African operations in the coming years.Arnold Ekpe, former chief executive of pan-African lender Ecobank Transnational, will chair the Atlas Mara board which will include Diamond and Thakkar alongside Tonye Cole, co-founder of Sahara Group, and Rachel Robbins, lead lawyer for the World Bank’s International Finance Corporation.Diamond left Barclays in July 2012. It was the first bank fined for its involvement in Libor rate-rigging, but since then Switzerland’s UBS, Royal Bank of Scotland and Dutch lender Rabobank have received bigger fines.Diamond was praised for building up Barclays’ investment bank into a global power over more than a decade before taking over as chief executive in 2011. However, evidence of a strained relationship with regulators emerged following his departure with former Bank of England governor Mervyn King telling lawmakers the bank had been "sailing too close to the wind across a wide number of areas”.Since leaving Barclays, Diamond has kept a relatively low profile, but he has made no secret of his plans to invest in Africa, where his charity - the Diamond Family Foundation - supports a range of projects.