Simon Firth

Simon Firth is one of the leading authorities on the law of derivatives, with over 35 years’ experience of this subject. He is the author of Firth on Derivatives Law and Practice, this is the leading textbook on English derivatives law, which is frequently cited in the courts and has been followed in several important derivatives cases. He has extensive experience in advising about the interpretation of the ISDA Master Agreement and other standard form documentation and many of his opinions have been relied on by the market generally.

He is a member of the Financial Markets Law Committee, which is responsible for identifying issues of legal uncertainty in the wholesale financial markets. He is also a Visiting Professor at the University of Law. 

Work highlights

Simon led the team advising the English administrators of the Lehman Brothers companies on their derivatives, repo and stock lending positions and has been involved in some of the market’s most significant cases involving derivatives. These include:

• Lomas v JFB Firth Rixson, Inc., the leading case on the ISDA Master Agreement; and
• Re Lehman Brothers International (Europe) (No.6), which established a number of important principles regarding the close-out provisions of the ISDA Master Agreement

He is responsible for the updating of ISDA’s English law netting and collateral opinions and was part of the team that drafted the 2021 ISDA Interest Rate Definitions. In 2024 he undertook a review, at the request of ISDA, of the operation of the Credit Derivatives Determinations Committees. His report made a number of recommendations for the reform of the determinations process.

Simon is a Visiting Professor at the University of Law. He is also a member of the Financial Markets Law Committee, an independent committee of legal experts responsible for identifying issues of legal uncertainty in the wholesale financial markets.

Simon frequently writes and speaks about legal issues in the financial markets. He is the author of:

• Firth on Derivatives Law and Practice, Sweet & Maxwell (looseleaf), the leading text book on English derivatives law; and
• “The English Law Treatment of Lehman’s Derivatives Positions”, in Bank Failure: Lessons from Lehman Brothers, Oxford University Press, March 2017

Simon studied Jurisprudence at Christ Church, Oxford University.