Read Marcus Binney's criticism of the stadium design

Watch the London 2012 promotional video

The final design of the 2012 Olympic Stadium, with its sunken bowl, removable seating and “steel crown” roof, was unveiled by Lord Coe yesterday to muted applause.

The stadium in Stratford, East London, costing £500 million, will have 25,000 permanent seats sunk into the main structure, 55,000 temporary seats which can be sold off after the Games and a roof covering two thirds of the spectators.

But there were still question marks over how much the athletics arena would cost, part of an estimated £9.3 billion bill for the Olympics, and its legacy for Londoners.

Mainly owing to inflation, VAT and contingency costs, the cost of the stadium has already almost doubled from £280m to £496 million since the original bid to host the Olympics in 2004.

But John Armitt, chairman of the Olympic Delivery Autority, admitted yesterday that it could rise further. Any overrun would have to be shared by the taxpayer and the contractors, said ODA officials.

The structure has been substantially revised since the first designs back in 2004, with silver shell casings, and is less spectacular than the Beijing or Sydney venues. The latest modest version has a mosaic fabric “wrap” around the walls of the stadium, depicting athletes and countries’ flags, which could be cut up and made into memorabilia bags after the event.

Coloured pods will be positioned around the stadium with facilities for spectators such as food and drink stalls and screens to watch other events. The roof is said to allow no more than the optimum wind speeds to break Olympic and world records.

Lord Coe, chairman of the Olympic Organising Committee yesterday described the structure as a “stadium for a completely new era that will be inspiring and have a lasting legacy”.

Rob Sheard, senior principal architect, conceded the design “was not screaming from the rooftops” but was a clever solution to the challenges set by the ODA.

A prerequisite of the original design was that it should shrink after 2012 from 80,000 to 25,000 seats, while still being used for track and field events. Much of the structure, would therefore be taken down and sold or leased after 2012 to other UK sports venues.

The temporary steel-and-concrete structure, providing seating for 55,000 spectators, can if necessary be split into ten modules of 5,000 seats and hived off separately.

Building work is expected to start next April or May and completed in 2011 to allow time for test events to be held. Sir Robert McAlpine Ltd heads the Team Stadium contract in partnership with HoK Sport architects and Buro Happold engineers among others.

Tessa Jowell, the Olympics Minister, said negotiations were still continuing over the “anchor tenant” who would take over the stadium in its reduced form and whether other community buildings would be built around the main arena.

Options are said to include a school, university faculties, a skills academy, a football or rugby club in the winter and athletics club in the summer. As with the Millennium Dome, the stadium could also be managed by a commercial company, which would decide which community facilities would be built.

She disclosed that £350m would be spent on adapting the Olympic venues for use after 2012. And she said there would be a further “legacy budget” for the running costs of facilities after the 2012 Games although this could not be determined for some time.

Hugh Robertson, shadow Olympics Minister said: “It is vital that the Government nail down the post games legacy use as soon as possible. £500 million is a great deal of public money, and we were all assured that the legacy would be built into the design stage, so it is vital that key anchor tenants are signed up as soon as possible.”

However, Ken Livingstone, the Mayor of London said: “It is really inconceivable that anyone would have signed up to occupy a stadium before they could see it.”