Mr Walker-Arnott gained extensive experience as a commercial lawyer at the international law firm Herbert Smith, where he was Senior Partner and is currently a consultant. He has served as a non-executive director of two listed companies in the manufacturing and insurance industries.
He was a member of the departmental committee (the Cork Committee) that reviewed insolvency law and whose recommendations are enshrined in the current law. He was one of the first three outsiders (nominated by the Bank of England) to sit on the governing body of the Lloyds insurance market. From 2003 to 2004 he sat on the small advisory group assisting Sir David Clementi in his review of the regulatory framework for legal services, implemented as the Legal Services Act 2007. He has served as on the Board of Governors of The Wellcome Trust since 2000 and is a Visiting Professor at University College London, where he teaches company law.