Born in Nelson, Newcombe grew up in Auckland, then moved to Australia (first Brisbane, then Melbourne) in 1963, and subsequently moved to Europe in 1968. He competed in the 500cc Grand Prix World Championship finishing second to Phil Read in the 1973 season.

Along with fellow racer, John Dodds, he developed a motorcycle using a two-stroke outboard motor designed by Dieter König. He and the König were the first to challenge the dominance of the MV Agustas after the departure of Honda from Grand Prix competition at the end of the 1967 season. In contrast to his main competitors, Newcombe was credited with the distinction of developing, building, maintaining, and riding the König machine in competition.

On 11 August 1973, Newcombe was seriously injured at a non-championship event at Silverstone at Stowe Corner. After taking his customary walk of the track prior to the event, Newcombe had requested that hay bales be positioned on the outside of Stowe Corner before the race but race officials refused, stating they were "not required". In the race itself, Newcombe slid off the circuit at that very corner, and collided with the concrete barrier. He died from his severe head injuries three days later. He was survived by his wife Janeen who was supporting him on tour, and their son Mark (aged four at the time).

...
Wikipedia