An empty tourist double-decker sightseeing bus passes behind a 'Yes' ('Nai') referendum poster in central Athens. On 26 June 2015 Greek Prime Minister Alexis Tsipras called a surprise referendum to ask the Greek people whether they would accept further austerity imposed by the 'troika' (the International Monetary Fund, the European Central Bank and the European Commission) - ie a 'yes' vote - or reject further austerity and risk being ejected from the Eurozone - or a 'no' vote. The referendum is to be held on 5 July.
