Simon Gleeson was a partner at Clifford Chance in London. He is described by all of the major directories as one of the world's leading experts in financial services and banking regulation, capital markets and derivatives.

In addition to his private practice, Simon is heavily engaged in the development of law and policy in finance. He is generally regarded as one of the intellectual leaders in the post-crisis reform of financial regulatory and resolution law, having worked with national and international bodies to develop the "bail-in" concept. He has been called to give evidence to UK and EU parliamentary committees, and has worked closely with other legislators around the world (including G-20 governments). He advised the World Economic Forum on its 2009 Report on The New Global Financial Architecture, and was heavily involved in the establishment of the UK's Banking Standards Board.

Simon has lectured at Harvard, Oxford, Cambridge and Edinburgh Universities, and at King's College London, the LSE and QMU London. He was a visiting fellow of All Souls in 2017-18.