He was educated at the Dragon School and Street Edward"s School, Oxford before reading Jurisprudence at Jesus College, Oxford.
He joined Norton Rose and qualified as a solicitor in 1972, becoming a Partner in 1977 and then holding the position of Chairman and Senior Partner between 1997 and 2003. He was elected as a City Alderman in 2001 and then Sheriff of London in 2006. He became the 680th Lord Mayor in 2007, being only the eighth Welsh Lord Mayor in the City of London"s history, and the first to have a Welsh heraldic motto.
Upon the completion of his year of office Lewis was knighted in the 2009 New Year Honours List.