
Top athletes Sir Chris Hoy, Michael Johnson and John Amaechi will be on hand to help mark the milestone, showcasing the latest progress on the Olympic Park.
They will be joined by local school pupils to ride the first lap of the Velodrome; sprint on a temporary track in the Olympic Stadium; and shoot the first hoop in the Basketball Arena respectively.
Seventy members of Visa Team 2012 - London 2012 hopefuls - will also walk over the main bridge into the Olympic Park.
Dance group Diversity, Olympic champion Sally Gunnell and CBeebies presenter Cerrie Burnell are on hand to launch the official Games-time volunteering programme. Up to 70,000 'London 2012 Games Makers' will be needed to make the Games happen.
The Mayor of London launches the 'London Ambassador' programme too, which will recruit 8,000 volunteers to help guide the millions of visitors who will travel to London for the Games get around and enjoy a truly memorable stay in the capital.
A number of London 2012 partners and licensees are also joining in the two years to go celebrations, including a giant screen and activities in Trafalgar Square hosted by Panasonic; and the first soft toys of Olympic mascot Wenlock going on sale.
Plan your Games
With just two years to go, planning well underway and athletes in training, the London 2012 Organising Committee is calling on the UK public to start planning their Games: