Mr Selmayr has spent much of his career surrounded by the bureaucracy of Brussels. He began his career as a lobbyist before working under Elmar Brok, an influential German MEP, then in 2004 became a spokesman for Viviane Reding, a former commissioner.
He subsequently developed a reputation as a formidable operator with a relentless work ethic, pushing aside Brussels veterans as he promoted his vision of a «United States of Europe».
In 2014 he ran Mr Juncker’s campaign for the presidency of the European Commission. At the time Mr Juncker was considered an outsider, opposed by Britain and Germany.