Short and in French but interesting; I've learned that the first market for Triumph was the US already in the 60s and all Hollywood actors had to ride on a Triumph.
The first Rocket 3 was really lighter, belonged to BSA but was killed by the Japanese tsunami and in particular when the Honda 750 arrived. However the 3 cylinders Rocket 3 developed by Triumph won the Tourist Trophy, the Bold d'Or and even Daytona in 1971 vs the Honda and other Japanese bikes ! :
Triumph Rocket 3 : Dragster sur deux roues - Automoto | TF1