[4] Launched in 1959 by Triumph as "The Best Motorcycle in the World", the Bonneville T120 was aimed mainly at the lucrative US market where enthusiasts were demanding extra performance.

[8] Initially produced with a pre-unit construction engine which enabled the bike to achieve 115 mph (185 km/h) without further modification, the power tended to induce high speed wobbles from the single downtube frame,[4] so in 1963 a stiffer and more compact unit construction model was introduced, with additional bracing at the steering head and swinging arm.

[4] The steering angle was altered and improved forks were fitted a couple of years later, which, together with the increased stiffness enabled overall performance to match that of the Bonneville's rivals.

Entered by Triumph dealers including Alec Bennet and Kings Motors (run by owner Stan Hailwood, Mike Hailwood's father) with bikes supplied from the factory, in this first race they finished 2nd, with riders Tony Godfrey/John Holder (behind a BMW) and 4th, riders Arthur Burton/Charles Erskine; the beginning of a successful era of Triumph motorcycle racing.

In September 1955, Allen had achieved a two-way average speed of 193.3 mph (311 km/h) on his special motorcycle the "Devil's Arrow", a 650 cc twin-cylinder Triumph engine fuelled by methanol in a unique 'streamliner' fairing.

Allen's speed was ratified as a record by the American Motorcycle Association but not by the world authority, the FIM, as no official observers were present.

German motorcycle firm NSU took the record the following year, so Allen and his team returned to Bonneville in September 1956 and won it back with an average speed of 214.17 mph (344 km/h).

In 1962 Bill Johnson set a two-way average of 230.269 mph (370.5 km/h) over a measured mile, riding a 667 cc 'streamliner' whose design was based on the American X-15 rocket plane.