Driving the Lotus 25, Spence qualified ninth and was classified 13th in the race despite the car's oil pressure fading near the end, while team-mate Jim Clark took the win and with it the Drivers' Championship.

However, shortly before the British Grand Prix, Arundell suffered a severe accident in an F2 race at Reims-Gueux, and Spence was called up to replace him in the F1 team for the rest of the season.

Before the Championship began in May at Monaco, Spence signed for the privateer Reg Parnell Racing team, but the BRM-powered Lotus 25 he drove was elderly and unreliable and he finished only twice, in the Netherlands and Italy, although he was fifth on both occasions.

For 1967 the great advance was the addition of aerodynamic wings to the rear of his cars, generating extra downforce to improve grip levels and hence cornering speeds.

Following Clark's death at Hockenheim in early April 1968,[3][4] Colin Chapman invited Spence back to Lotus as part of their Indianapolis 500 team, with the race in late May.

During practice at the Indianapolis Motor Speedway on Tuesday, 7 May, Spence, driving the #60 Lotus 56 turbocar (later qualified and driven by Joe Leonard), ran a lap of 169.555 mph (272.9 km/h) – fastest of the month and second-fastest in track history.

[5][6] Later in the afternoon, Colin Chapman was asked by Andy Granatelli if Spence could take out turbocar #30 for a test run after driver Greg Weld had difficulty getting the car up to speed.

The right-front wheel of the Lotus swiveled backwards into the cockpit and struck Spence on the helmet; he died in the hospital later that evening at 9:45 pm from massive head injuries.