From Wogew excellent blog:
Paul McCartney revisits the original Cavern Club, 1968Posing with "Curiosity Shop" at the Cavern stage. Photo by Linda Eastman.
When Sir Paul McCartney made an impromptu visit to the Cavern in 1968 he made the owner promise not to tell the press.
Paul made a surprise visit to the Cavern Club with his then girlfriend Linda Eastman on October 25, 1968.
Paul called alone at approximately noon and asked if he could call back later with Linda as he was on his way to drop off a record player to his stepsister Ruth on the Wirral. Alf Geoghegan, owner of the Cavern, asked Paul if he minded if he took some photographs of the occasion. Paul agreed as long as the press were not informed.
Alf realised that he did not have a camera with him and he walked around the corner to Photo-Optics, a photographic shop in North John Street and purchased a Yashica Camera to record the occasion. The salesman accompanied Alf back to the Cavern to set the expo-sure and shutter speed not having been told who was going to be photographed. Paul returned with Linda and when Alf picked up the camera to take the photographs, Linda said "I'm a good photographer, I'll take them for you." She photographed Paul with Debbie Geoghegan, Alf's daughter, with Paddy Delaney, the Cavern doorman and on stage with Curiosity Shop, a group who were managed by Alf who were rehearsing at the club at the time.
Paul then joined the group on stage and played the drums saying that he had always wanted to be a drummer. Also on the photographs can be seen Alf Geoghegan and DJ Billy Butler.