The roof of the main 2012 Olympic stadium began going up this week, a symbolic stage in Britain's preparations for the Games, but doubts remain over a long-term tenant.
The first 30-metre steel section was lifted into place on the showpiece 700 million dollar stadium, taking its height to almost 37 metres (120 ft) above podium level.
The roof should be finished in nine months' time and the entire stadium by the Summer of 2011.
The stadium will host track and field events as well as the opening and closing ceremonies.
However concern remains about its legacy after leading football clubs ruled out moving in because of its size and the retention of the athletics track around the pitch.
The stadium's 80,000-seating capacity will be reduced to 25,000 after the Games, too few for a Premier League football club, and fans do not like being so far from the field of play.