Upon completion of his doctorate degree in 1967, Nwankwo was unable to return to Nigeria as the Civil War just began, he decided to stay in London and eke out a living as a lecturer at City of London College. He taught at the college for five years until he returned to Nigeria in 1972 when he was recruited to start a department of finance at UNILAG being sponsored by the United Bank for Africa. In Nigeria, Nwankwo called for a post-colonial review of the Nigerian financial system and adoption of practices that is easily adaptable to the peculiarities of indigenous values and systems.