London Mayor Boris Johnson tries a test ride in the velodrome under construction, in the Olympic Park, east London, Britain, July 27, 2010. Tuesday marks exactly two years to go until the opening ceremony of the London 2012 Olympic Games. The London Organising Committee of the Olympic Games and Paralympic Games (LOCOG) and the London City Hall launched the Volunteering Programme and the flagship shop of London 2012 on the day. [Xinhua/LOCOG]