Bourdais battled with Tracy before the Canadian's engine blew
Frenchman Sebastien Bourdais has won his first Cart race, ending the dominance of Canadian Paul Tracy in this year's Champ Car World Series.
A tight tactical battle between the two was resolved when Tracy's engine blew up on the 119th of 165 laps at the Brands Hatch track in Kent.
Bourdais' Newman-Haas team-mate Bruno Junqueira was second, closing the gap to Tracy at the top of the championship to just 11 points - Champ Car gives 20 points for a win.
Mexican Mario Dominguez was third, followed by Spaniard Oriol Servia, Canada's Patrick Carpentier and Michel Jourdain of Mexico.
Briton Darren Manning was 10th after an off-track excursion at Paddock Hill Bend early in the race.
Before the retirement of Forsythe Racing driver Tracy, who had won the first three races of the season, Bourdais appeared to have won his tussle with his veteran rival.
Tracy, who was on pole position, led the first stint of the race, but Bourdais sneaked ahead at the first stops by staying out slightly longer.
Tracy has seen his series lead slashed
The exra time out on the track with low fuel gave the rookie just enough of an advantage to get out ahead.
"We made it. It was difficult but we made it," Bourdais said.
"We would probably have been the winner in two races already. It's been frustrating after the
first events. The worm turned. Paul had trouble today and we got a bit lucky."
Tracy's engine started to pump out blue smoke just as the race was building to a crescendo around the second pit stops.
Tracy still left the UK with a points lead in the Champ Car World Series, but his advantage has now been slashed by his rivals.
Tracy said: "We would have been content to finish on the podium, but
the engine let go on us."
Leading results from London Champ Car Trophy at Brands Hatch:
1 Sebastien Bourdais (Fra) 165 laps, 105.412 mph
2 Bruno Junqeuira (Bra) 7.835 seconds behind
3 Mario Dominguez (Mex) +11.524
4 Oriol Servia (Spa) +14.385
5 Patrick Carpentier (Can) +15.035
6 Michel Jourdain (Mex) +30.703
7 Roberto Moreno (Bra) +36.997
8 Alex Tagliani (Can) +38.762
9 Mario Haberfeld (Bra) one lap behind
10 Darren Manning (GB) one lap behind