Can London's big top become the main attraction?

As designed by HOK Sport, the stadium has a simple elliptical shape dominated by a wrap-around fabric curtain and a delicate structure of repetitive x-shapes in tubular steel.

All the flamboyance promised in 2004 by a feasibility sketch study by Foreign Office Architects has been stripped away. Instead, the plain ellipitical form and curtain wrapping give the stadium the flavour of a circus big top rather than a four-yearly pinnacle of world sport.

Even so, there is an underlying logic to the design. The curtains and flimsy structure are all expendable: they will be whisked away to convert the 80 000-seat Olympic stadium to a permanent stadium of just 25,000 seats.

The smaller permanent portion of the stadium takes the form of a bowl sunk into the ground. The larger temporary portion rises above this and is concealed behind the fabric curtain and topped by a canopy roof. Sporting images will be projected on to the fabric curtain.

The Olympic Delivery Authority claims that the design of an Olympic stadium with such as large demountable element is unprecedented. The fabric curtain and tubular steel frame are both designed and specified to be recycled after demolition.

After the completion of the Olympic Games in 2012, the building will be handed over to the London Development Agency and leased to a private company. The design and appearance of the permanent stadium will not be revealed until the private leaseholder is appointed next year.