Vincent was a small volume British manufacturer of motorcycles from 1928-1955. Depending on one’s definition of “standard,” Vincent produced the fastest “standard” motorcycle in the world until the late ‘60s/early ‘70s. Vincent made 500cc singles and 1,000cc V-twins. The Rapide was Vincent’s base model V-twin, the Black Shadow was a high performance version of the Rapide, and the Black Lightning was a racing version. So, young James Adie probably rode a Black Shadow with the engine built to Lightning specs. (One of the best known motorcycle pictures ever is Rollie Free wearing swim trunks lying prone on a Black Lightning, setting a record of 150mph at Bonneville in 1948. See https://en.wikipedia.org/wiki/Vincent_Black_Lightning#/media/File:Rollie_Free,_record_run.jpg)