Question: who was prime minister when we joined the common market
Answer: The United Kingdom European Communities membership referendum , also known as the Referendum on the European Community ( Common Market ) , the Common Market referendum and EEC membership referendum took place on 5 June 1975 in the United Kingdom to gauge support for the country 's continued membership of the European Communities ( EC ) -- often known at the time as the `` European Community '' and the `` Common Market '' which it had entered on 1 January 1973 under the Conservative government of Edward Heath under the provisions of the Referendum Act 1975 .