Broadley's chassis was much lighter and sweeter-handling than the in-house RA273. The car initially performed impressively, winning in its first-ever World Championship race, the Italian Grand Prix at Monza. Driver John Surtees took the lead from Jim Clark's Lotus and Jack Brabham's Brabham on the final lap, after Clark ran out of fuel and Brabham ran wide. However, the RA300 flattered to deceive, and this would turn out to be the only lap that the car would lead. It remains the only F1 car ever to take its single victory in its first Grand Prix, and on the only lap it would ever lead.