Prototyped by Californian Norton Distributor Bob Blair using the Atlas 750 cc twin cylinder engine in a Matchless G85 CS (Competition Springframe) Reynolds 531 lightweight steel frame.

[3][better source needed] The aim was to achieve the best possible power-to-weight ratio, so all the cycle parts were made as light as possible, with a small alloy fuel tank.

[1] The new motorcycle was known as Project 11, and although testers of the prototype suggested that it should be called the Cheetah 45,[1] it was eventually shortened to P11 and built at the former Associated Motor Cycles factory in Woolwich, London, largely from spare parts.

[6] The availability of spare parts at the Norton-Villiers factory led to several changes of specification, and the P11, P11A and Ranger were produced with four different types of oil tanks (two alloy, two steel), 3.6 gallon and 2.2 gallon petrol tanks, different types of handlebars, forks and frames, two ignition systems and two different cylinder heads (with the last models produced using Norton Commando castings).

[1] By 1969, lighter two-stroke desert racers began to dominate the sport and the Norton Commando had started production and was selling well.