Jacomet studied history and worked at the Paris West University Nanterre La Défense. He was diplomatic adviser on the WEU staff from the Alfred Cahen administration (1985–1989) onwards. On 25 November 2009 he succeeded Javier Solana as Secretary-General of the Western European Union. Jacomet completed the task of finishing the transfer of the remaining WEU functions to the EU Commission and the closure of the organisation. The WEU dissolved on 30 June 2011. Jacomet died of cancer a few months later.
