Twenty-five of the franchises were purchased for the 2005 â `` 06 A1 Grand Prix season . It began on 25 September 2005 . Twenty-five of the franchises were purchased in time for the 2005 â `` 06 A1 Grand Prix season , which began on 25 September 2005 with the A1 Grand Prix of Nations Great Britain at the Brands Hatch circuit in Kent , United Kingdom .