The Diane Warwick version was the one I knew best before Naked Eyes.
And the best version for my money. The way she kicks it upstairs at the key change... incredble. It didn't chart well for her, though.
That her version didn't chart well really surprised me. I can only assume that back in the 60s and 70s, when radio stations had a bit more local control over what they played, whatever station I/my parents listened to promoted that version and/or it was something of a regional hit.