He was not a household name, certainly not in the US, but he was a major figure for a short while in the mid 70s. Talented as hell as a songwriter, prickly and over confident in his personality, he kinda was the thread that connected glam to what became early post-punk on the late 70s.
In so many ways he had more in common with The Kinks and Ray Davies than glam standards David Bowie and Marc Nolan (imo). His sound was very English in a similar way. He was famous for not allowing electric guitar in his music in the beginning.
Cockney Rebel's first three albums (self-titled in '73, Psychomodo in 74, and The Best year of our Lives, 74) are definitely worth checking out. After that he had a solo career and played as Steve Harley & Cockney Rebel for a while.
And the song that really threw me off when I first heard it earlier in life when I was a much more impressionable young man, and really stayed with me: