He was Director of UKAEA Culham (2003-2008), with responsibility for the UK's fusion programme and for operation of the Joint European Torus (JET), Provost and President of University College London (1999-2002), Director General of CERN (1994-1998), and Chairman of Oxford Physics (1987-1992).
After completing his Doctorate in Oxford in 1967, he worked briefly in the Lebedev Physical Institute of the Academy of Sciences in Moscow, before spending periods at CERN and the Stanford Linear Accelerator Center, after which he returned to Oxford in 1974.
As Director of UKAEA Culham he developed and vigorously promoted the 'Fast Track' approach to the development of fusion power, which was officially adopted by the European Commission. During his mandate as Director General of CERN the Large Hadron Collider (LHC) was approved, construction started, and major contributions from Canada, India, Japan, the Russian Federation and the USA were negotiated, and CERN's flagship Large Electron Positron collider (LEP) was successfully upgraded.
As a theoretical particle physicist he worked mainly on the quark model and the theories of the strong and electro-weak forces, and how they can be tested experimentally. His contributions include developing ways to demonstrate the "reality" of quarks and gluons (the particles that transmit the string force that holds quarks together) in highly inelastic electron and neutrino scattering experiments, and showing that mathematical consistency requires any theory of the weak interactions to be based on a spontaneously broken gauge theory (list of publications).
He was Chairman of the Council of the world fusion project ITER (2007-09), the Consultative Committee for Euratom on Fusion (2003-09), the Advisory Committee on Mathematics Education (2002-04), and the CERN Scientific Policy Committee (1990-92), and has served as a Vice President of the Royal Society (2008-10) and on numerous other national and international advisory committees, including the UK Prime Minister's Advisory Committee on Science and Technology (1989-92).
Chris Llewellyn Smith has written and spoken widely on science funding, international scientific collaboration and energy issues. His scientific contributions and leadership have been recognised by awards and honours in seven countries on three continents.