John Surtees, driving a V-12 Ferrari, won a sensational Belgian Grand Prix at Spa-Francorchamps, the rain-soaked afternoon marred by a multi-car collision early on.
In practice, Jim Clark had a lucky escape when he narrowly avoided a collision with a road car on the track. "I was taking the hill from Eau Rouge at 130mph and taking my line through the bend when I came across this car moving at a quarter of my speed. It was all I could do to stay out of the trees."
The race started in the dry but midway through the first lap the heavens opened and left the road surface resembling polished glass, and a number of cars aquaplaned in various directions. Some were lucky and remained on the track, others less so. "One minute it was dry, the next it was covered in driving rain," Graham Hill told The Times. "One car started to spin and then the others as they tried to avoid it. Then cars started hitting each other, with four eventually involved going in all directions."
"We just ran into a wall of water in the way it can rain only in southern Belgium," Stewart told Alan Henry in The Guardian almost three decades later. At 170mph, his BRM aquaplaned as he approached the right-hand Masta Kink. "First I hit a telegraph pole and then a woodcutter's cottage and I finished up in the outside basement of a farm building. The car ended up shaped like a banana and I was still trapped inside it.
"The fuel tank had totally ruptured inwardly and the monocoque literally filled up with fuel. It was sloshing around in the cockpit. The instrument panel was smashed, ripped off and found 200 metres from the car but the electric fuel pump was still working away. The steering wheel wouldn't come off and I couldn't get out."
Seconds later Stewart's team-mate Hill had slid off at the same spot but with less spectacular results, even though he careered into straw bales backwards at 130mph. As he tried to get his car back onto the track - he could have continued but eventually retired as he had lost so much time - he noticed the wreckage of Stewart's car and ran to see what had happened. On discovering the stricken Stewart, Hill quipped he looked "very second hand". He managed to turn off the fuel pump and started trying to free him. He was joined soon after by Bob Bondurant who had also spun off and overturned.
The pair worked furiously to try to extricate him with fuel still swamping them and the vehicle. One spark and all three men would have been engulfed in a fireball.
It took them 25 minutes to extract Stewart from the wreck, during which time no marshals appeared, but finally, with the aid of a toolkit borrowed from a spectator, they unscrewed the steering wheel, pulled him clear and carried him to a barn.
Stewart asked Hill to remove his clothing, aware that his fuel-soaked race suit remained a major risk and was also burning his skin. "Then these nuns came in," Stewart said, "and spotting a naked man in the back of a hay truck put my clothes back on. Having found an ambulance, Graham came back in and took my clothes back off again."
Even then Stewart's ordeal was not over. He was carefully loaded into the old ambulance which took him to what passed as a medical centre and left him there on a canvas stretcher. "There were no doctors," he recalled. "I was left on a stretcher, on the floor, surrounded by cigarette ends. It was filthy."
He was eventually loaded into another ambulance which set off for the hospital in Liege with a police escort. However, en route the escort became detached from the ambulance, and the driver then got lost as he did not know the way.
Amazingly, Stewart was the only serious casualty of the afternoon, even though the rain continued to pour. Seven cars were eliminated by the first-lap chaos, while Jim Clark was left sitting on the grid even though his mechanics had spent all night working to get his Lotus ready.
Jochen Rindt led for all but four laps, at which point John Surtees surged past and within a lap he had opened up an 11-second lead, which he had extended to 42 seconds by the finish. Third placed Lorenzo Bandini was more than a lap behind.
It was a short-lived celebration for Ferrari. Soon after Surtees became embroiled in a row with the team manager and walked out, switching to Cooper for the remainder of the season.