Who was the first driver to have held the Formula 1 and the CART Indy Car World Series titles at the same time?

Nigel Ernest James Mansell (born 8 August 1953) is a British former racing driver who won both the Formula One World Championship (1992) and the CART Indy Car World Series (1993). Mansell was the reigning F1 champion when he moved over to CART, becoming the first person to win the CART title in his debut season, and making him the only person to hold both the World Drivers Championship and the American open-wheel National Championship simultaneously.

His career in Formula One spanned 15 seasons, with his final two full seasons of top-level racing being spent in the CART series. Mansell is the second most successful British Formula One driver of all time in terms of race wins with 31 victories, and is seventh overall on the Formula One race winners list behind Michael Schumacher, Lewis Hamilton, Alain Prost, Sebastian Vettel, Ayrton Senna and Fernando Alonso. He held the record for the most number of poles set in a single season, which was broken in 2011 by Sebastian Vettel.