Member of the team that developed one of the first computerized cash machines in Essex, England, Cleaver began his career as a Systems Engineer with IBM, UK Ltd. in 1962, holding many positions within IBM in areas ranging from marketing, product management and production scheduling; but mostly in line management. He studied Literae Humaniores at Trinity College, Oxford, graduating in 1962. He was part of the team in the 1960s that developed one of the first computerized cash machines in Essex, England.
Cleaver was named General Manager in 1983, Chief Executive in 1986 and Chairman and Chief Executive in 1990. He retired from IBM in 1994.
He became Chairman of the United Kingdom Atomic Energy Authority in 1993. In 1996 he led the privatization and subsequent flotation of UKAEA's commercial activities, becoming Chairman of AEA Technology Plc; a position he held until the end of 2001. Cleaver served as Chairman of the Nuclear Decommissioning Authority from 2004 to 2007 and was Chairman of the Medical Research Council. He served on the Boards of Smith and Nephew, Lockheed Martin UK and IX Europe.
In the field of education, Cleaver chaired the Governors of Birkbeck, University of London and the Royal College of Music, both in London. In August 2007, he was appointed Chairman of EngineeringUK (formerly the Engineering and Technology Board (ETB)) in the UK, where he chaired the project to launch the first UK Young Scientists and Engineers Fair, a three-day event in March called "The Big Bang" designed to inspire the next generation of scientists and engineers.
He went on to serve as Chairman of recruitment company SThree and financial wrap provider, Novia Financial. Cleaver held an extensive number of positions as Chairman and Director of a variety of international and national companies and institutions as well as governmental entities. He also founded and chaired numerous establishments, including serving as the Founding Chairman of Business in the Environment.
