This was supposedly a quote from Rem Fowler upon winning the 1907 Isle of Man TT. It was used in Norton advertising the following year with a picture of the new Norton and under it " My success is due to the unapproachable Norton". It became the Norton slogan for years to come.
And no, I wasn't around then, I read it in Mick Woollett's "Norton, The Complete Illustrated History". It's a good read on the early history of the marque.