Supporters of far-right Golden Dawn party outside the appeals court in Athens, Greece in 2014. The neo-fascist group recorded 500,000 votes in last September’s general election, seven per cent of the poll, returning 18 MPs. Photograph: Simela Pantzartzi/EPA

David Cameron says that if the referendum on British membership of the European Union returns a majority for leaving, it would take two years to negot(...)