What happened this day in history: December 6
1768 - The first edition of the Encyclopedia Brittanica was published, in Scotland.
1774 - Australia became the first nation to introduce a state education system.
1897 - London became the world’s first city to host licensed taxicabs.
1922 - One year to the day after the signing of the Anglo-Irish Treaty, the Irish Free State came into existence.
1957 - The first American attempt to launch a satellite failed when it exploded on take off.
1975 - Armed IRA men on the run from police burst into a central London flat and took two people hostage. The Balcombe Street siege lasted for six days.
1983 - Medical history was made as the first heart and lung transplant operation performed in Britain was successfully carried out. Swedish journalist, Lars Ljungberg survived for 13 days after the operation.
2005 - David Cameron was elected as the new Conservative leader by a margin of more than two to one over David Davis.