Complex sentence: It was, in fact, so unusual that Davis had to persuade the Roost's manager, Ralph Watkins, to allow the sign to be worded in this way; he prevailed only with the help of Monte Kay, the club's artistic director.
Split into simpler sentences: It was, in fact, so unusual that Davis had to persuade the Roost's manager, Ralph Watkins, to word the sign this way. He prevailed only with the help of Monte Kay, the club's artistic director.