London was ahead of previous host cities in its preparations for the Olympics and had made impressive progress in the last year, Denis Oswald, head of an IOC inspection of the 2012 site, has said.

Oswald began a three-day visit of the east London venues on Tuesday with a close-up inspection of the Olympic stadium that is already rising on the skyline.

"We have a stadium, we are sure. It was not necessarily the case in some of the previous Games. So it's very relaxing," Oswald, chairman of the IOC's Coordination Commission, told reporters after being shown around by 2012 chief Sebastian Coe.

The stadium, which will cost about £540 million, almost double the original forecast, will have a capacity of 80,000 during the Olympics before the top tiers are removed and it is scaled back to a 25,000-seater.

No full-time use for the stadium after the Games has been decided yet, although it will house a school and a National Skills Academy.

With the big five venues - the stadium, Velodrome, Aquatics Centre, Village and Broadcast and Media Centre - all under way, the IOC's main concern will be to assess the soaring costs of the project and the impact of the credit crunch.

The government has already been forced to release contingency funds to keep the Village project on track after private investment dried up, although it says the £9.3 billion overall budget will not rise.