The winner in Cardiff will progress to the Super Prix final, taking gate 3 and the white helmet colour.
Edward Kennett was nominated as a wild card after he finished 2nd at the 2008 British Speedway Championship.
Tai Woffinden and Simon Stead were the next highest finishing non-Grand Prix riders and both will be track reserves at Cardiff.
[3] Jason Crump from Australia was the winner of the British Grand Prix, he finished ahead of second placed Greg Hancock of the United States.
Nicki Pedersen fell in the final and therefore scored 0 points from the race, but still took third place on the podium.