Premise: The 8th Race of Champions was a non-Championship motor race, run to Formula One rules, held on 18 March 1973 at Brands Hatch circuit in Kent, UK. The race included several entrants in Formula 5000 cars and was won by Peter Gethin in a Chevron-Chevrolet B24 '72-05'. This was the only race other than the poorly-attended 1969 Madrid Grand Prix in which a Formula 5000 car beat a Formula One car.
Hypothesis: Unlike in this century, not only once, but twice within a five year span in the Twentieth Century, has a Formula Five Thousand car prevailed against a Formula 1 racing vehicle.