Although it stands more than 60m high, the north intermediate tower is the smallest of the three towers to be built. The other two, to be 90m high, should be completed by late spring 2012.
The cable car, called the Emirates Air Line under a £36m sponsorship deal with a Middle Eastern airline, is being built by a consortium headed by Mace.
The team also includes steelwork contractor Watson Steel, designers, URS Scott Wilson, Buro Happold and Aedas, and cable car specialist Dopplemayr. The project involves stretching 50mm diameter steel cables more than one kilometre between the steel towers. The cables will carry 34 cabins, each capable of carrying 10 passengers, and provide a link connecting the Greenwich Peninsula and the O2 arena with the Royal Victoria Docks and the ExCeL conference centre.
Each of the towers is made up of approximately 6,500 steel sections. A complex helical structure was put forward by Mace and developed by Aedas and Watson Steel.
The first tower was built within days of its steel pieces being delivered to site from Watson’s Bolton fabrication centre.
Project director Matt Randall said "All credit goes to the project team who have been working round the clock seven days a week for the month of December to achieve this important milestone."