The Quarrymen at the Casbah Club in Liverpool. Might Paul possibly be serenading Cynthia Powell with a rendition of Elvis Presley's Wooden Heart in this photograph?
Here's a Hamburg-era Beatles oddity, actually an Elvis Presley song from 1960, that was very popular in Germany. And so naturally that meant that the very early Beatles learned and played it onstage in Hamburg. I remember reading somewhere years ago that this was a tune the young Paul McCartney sang at the time. Anyway, the song is Wooden Heart, a tune I frequently whistle to the wry amusement (or possibly annoyance?) of my German-speaking wife. Enjoy!