Four years of Formula One racing for underfunded teams led Brundle to seek a new challenge, and thus in 1988 he took a year out. Brundle had been associated with Jaguar since 1983, when he drove TWR-prepared Jaguar XJS touring cars in the European Touring Car Championship. From his two starts with the Jaguar team Brundle took two victories, the second in partnership with TWR owner Tom Walkinshaw. When Jaguar decided to return to the World Sportscar Championship and the American IMSA championship, in partnership with TWR, Walkinshaw chose Brundle as his lead driver. The team performed well in the 1988 World Sportscar Championship season, and Brundle won the world sportscar title with a record points haul. He also won the Daytona 24 Hours the same year. He became the test driver for Williams and stood in for Nigel Mansell at the 1988 Belgian Grand Prix, after Mansell was struck down with chickenpox. Brundle was to have driven Mansell's Williams-Judd again at the next race at Monza in Italy but prior IMSA commitments with TWR saw the drive go to fellow World Sportscar Championship contender Jean-Louis Schlesser instead (as no WSC race clashed with the Italian GP). Schlesser would infamously be involved in the incident which caused the retirement of McLaren's Ayrton Senna late in the race, handing the win to Ferrari's Gerhard Berger and causing McLaren's only loss of the season.