LONDON (AFP) Olympic greats with a clutch of gold medals were to give the emerging London 2012 stadiums a test run on Tuesday as the city marks two years to go until the starting gun is fired. The British capital was to show off its progress towards staging what organisers say will be a new kind of Olympics, with two years left on the clock till the opening ceremony. Rather than the regular attempt to outdo the previous Games, the 2012 chiefs are set on building a lasting sporting legacy for Britain and regenerating one of the most deprived parts of the country in an economic downturn. So while the venues may be less spectacular than Beijing 2008, and the fireworks fewer, London 2012 hopes to leave lasting urban infrastructure and housing rarely created by sports events. Organisers feel they are on track to produce a well-run Games on a strict budget, in keeping with the tough economic times. So they are keen to show off how the project is running to schedule as they hit the two-year milestone. US athletics hero Michael Johnson, who boasts four sprint gold medals from three Games, was to test out a temporary track in the 80,000-capacity Olympic Stadium. Its distinctive white crossed-girder architecture is well on the way to completion and the seats are already being fitted. British cyclist Chris Hoy, who won three golds in Beijing, was to become the first to test out the new Velopark, which he helped design. Its only two years since the Beijing Olympics and it has passed in a flash so Im sure the next two years are going to pass really quickly too, he told the BBC. The Olympics are always there at the back of your mind. Its the main reason why you train every day. Meanwhile John Amaechi, the British former NBA star with Orlando Magic and Utah Jazz, was to demonstrate some of his skills at the Basketball Arena, a temporary venue built with giant steel arches. Paul Deighton, the chief executive of London 2012 organisers LOCOG, told AFP they were proud of their progress so far. Were on schedule and on budget. Of course we have to be on schedule because July 27, 2012 is, for us, the mother of all immovable deadlines, he said. Construction is currently well within the events budget of 9.3 billion pounds (11 billion euros, 14.2 billion dollars). The figure includes 1.2 billion pounds of a contingency fund, which has yet to be used. Away from the Olympic Park on Tuesday, Londons main Trafalgar Square was to see up to 4,000 people per hour attending a day-long display of top-end technology to be deployed in 2012, with a 60 square metre screen showing off the days countdown events. There will also be interactive games and celebrity appearances, plus a 3D Future Zone with six special pods allowing people to watch Olympic footage in high definition. The square was the scene of wild celebrations in July 2005, when London edged out Paris for the right to host the Games. London Mayor Boris Johnson was using the two-year milestone to launch an appeal for 70,000 people to volunteer at the Games as everything from city guides to press officers. This is a once-in-a-lifetime opportunity. It is the great people of this country, with their warm welcome and 'can-do attitude, on whom the success of our Games will depend, he said. Organisers are hoping the Olympic magic will spread beyond London to the rest of Britain with a cultural programme hotting up over the next two years. Nearly 1,000 challenge events took place across Britain over the weekend to mark the two-year countdown, including sports, art, dance and exhibitions. But there were also warnings Tuesday that the host nation could run into difficulties at the Games. An official said half Britains Olympic sports could face funding cuts if the budget for the government sports agency was slashed. Peter Keen, director of performance at the agency UK Sport and charged with improving Britains performance at the Games, told the Guardian paper that support would be focused on athletes most likely to win medals. And so if that means we can only fund half the sports then thats all we can do, he said.