In The Days Before Rock 'n' Roll Lyrics

Lyric discussion by benjazz 

Cover art for In The Days Before Rock 'n' Roll lyrics by Van Morrison

You may be correct about the reference to access to rock & roll via the radio, but I don't know get the connection to Lester Piggott, the most(?) successful English horse racing jockey. (Without the written lyrics, many think he's singing "Wilson Picket"). So who can explain the mix of Piggott and early rock & rollers? And who's Justin?