Task: Question Generation
Input (English): The Greater London Council was abolished in 1986, which left London as the only large metropolis in the world without a central administration. In 2000, London-wide government was restored, with the creation of the Greater London Authority. To celebrate the start of the 21st century, the Millennium Dome, London Eye and Millennium Bridge were constructed. On 6 July 2005 London was awarded the 2012 Summer Olympics, making London the first city to stage the Olympic Games three times. In January 2015, Greater London's population was estimated to be 8.63 million, the highest level since 1939.
Output (English): The population of Greater London in January 2015 was its greatest since what year?