Kenny Roberts took the 500cc world championship from Barry Sheene in his first season in Grand Prix racing. He was the favorite to repeat as winner the next year but was badly injured in a preseason testing crash and missed the first round.
Sheene won that first race and felt confident of the season ahead but against all odds, Roberts came back to win the second round. For the rest of the season, Roberts battled the lingering effect of his injury while Sheene suffered from a few mechanical problems. With two races to go, the championship battle moved to Silverstone. That British Grand Prix was one of the best races ever. Once Roberts and Sheene had got past early leader Will Hartog, they traded the lead almost every lap. Roberts won by a fraction of a second and won the overall championship that year, thoroughly demoralizing Sheene.
Watching this marvelous YouTube clip (was it pulled from a BBC broadcast?) I'm struck by the presence of two other interesting footnotes to this race. Note the presence on the grid of a bike that's actually part of the film 'Silver Dream Racer' and of two Honda NR500 oval-piston four-strokes. None of them had much luck in the race. Roger Marshall, riding the Silver Dream for actor/pop star David Essex had a problem with his fuel cap. Mick Grant crashed his NR500 when it leaked oil onto his rear tire in the first lap. Katayama pulled off the course when the second Honda started missing, then lost its front brake.