Wikipedia
Thundersports was a variety of sports car racing introduced by John Webb of Brands Hatch fame.
Webb saw it as a replacement for the Aurora AFX Formula One championship as a spectacular class that could headline national-level meetings, and a partner for the Thundersaloons series for silhouette-bodied touring cars.
Thundersports was essentially a sports-car version of Formula Libre with cars from Sports 2000, Group 5, Group 6, Can-Am, Group C and various other prototype categories all eligible; a number of hybrid cars appeared in the series. Even the odd Clubmans car appeared.
The series ran from 1983 to 1989, with grids slumping from 1983's average of around 20 to about 10 cars by the end. When the series was terminated it was effectively replaced by a short-lived BRDC C2 Championship for prototypes.