Wall (pictured) has been at the centre of Britain’s relations with the EU for 35 years. He spent five years as UK ambassador to the European Union in Brussels, and four years as EU adviser to Prime Minister Tony Blair. He was also responsible for running the Foreign Office’s European department and spent two years as Britain’s ambassador to Portugal.
In addition, Wall was foreign policy adviser to Prime Minister John Major.
He is the author of 'Britain and Europe – A Stranger in Europe', published in 2008, and, as official historian for the Cabinet Office, is currently working on the second volume of 'The Official History of Britain and the European Community'.
Based in Portland's London office, Wall will be part of the agency's pool of senior advisers, providing strategic advice to clients over the course of the referendum campaign. The role is not full-time, and there is no plan for him to stop working post-referendum.
Tim Allan, managing director, Portland, said: "The referendum on Britain’s membership of the European Union will be central to political and business issues next year. Sir Stephen has a huge amount of knowledge about European issues and is an expert on the complexities of negotiations with the EU."
Wall added: "The British referendum on European Union membership has implications for every company operating in the UK. It is a hot issue which requires cool analysis."