Question: What is the official name of the tower, previously known as Clock Tower, next to which a proposed Thames Airport was to be built in the 1930s?
Related documents: [0]  [DOC] Thames Airport was a proposed elevated airport during the 1930s that would have been constructed over the River Thames between Westminster Bridge and Lambeth Bridge. Not much is known about the proposed airport, except that it would have had an elevator to bring people to the flight deck, as well as room underneath for a hangar. It would have also been next to the nearby Big Ben and Palace of Westminster. [END] 
[1]  [DOC] Big Ben is the nickname for the Great Bell of the clock at the north end of the Palace of Westminster in London and is usually extended to refer to both the clock and the clock tower as well. The tower is officially known as Elizabeth Tower, renamed to celebrate the Diamond Jubilee of Elizabeth II in 2012; previously, it was known simply as the Clock Tower. [END] 
Answer: 
Elizabeth Tower
Elizabeth Tower