He led the team which restored the EAME operation to profitability, following which he launched an unsuccessful management buyout resulting in his departure in 1992.

Olisa then founded Interregnum, a technology merchant bank, leading it through its early growth, its entry into and exit from a joint venture with BDO Stoy Hayward, the AIM IPO in 2000.

More recently, he served as a non-executive director of Eurasian Natural Resources Corporation (ENRC) from 2007 and from which he was fired over governance concerns after which he coined the expression "More Soviet than City" to describe the way he and Sir Richard Sykes had been treated.

He also serves on the boards of, or is an adviser to, several privately held and innovative companies including the UK's leading corporate governance advisor Independent Audit.

[9] In 2009, The Sunday Times named him Not for Profit non-executive director of the year, and in 2016 he was voted number one in the Powerlist's Top 10 most influential British black people.

[21] His past appointments include serving as Master of the Worshipful Company of Information Technologists, Director of the Thomson Reuters Foundation, member of the Government's Women's Enterprise Taskforce; Governor of the Peabody Trust for ten years; non-executive director of the West Lambeth NHS Trust; and a start-up regulator twice: first as an inaugural Postal Services Commissioner, from 2001 to 2004, and as a board member of the Independent Parliamentary Standards Authority, the body charged with managing the expenses, pay and pensions of members of parliament.

On 19 March 2019, Olisa greeted Queen Elizabeth II and the Duchess of Cambridge at the opening of the newly refurbished Bush House.