Sir Paul McCartney was ignored by fellow tram passengers in New Orleans when he burst into song on a street car because they thought he was a busker.The 70-year-old star left fellow passengers bemused when he burst into a medley of some of The Beatles' biggest hits on a New Orleans street car, and the commuters did their bestto ignore him until they realised the crooner was none other than the legendary musician. Tram passenger Robert Senft told the Daily Mirror newspaper: "This guy got on the street car and started singing Beatles songs. Everyone was just ignoring him really because thereare a lot of buskers in this town."Then we realised it was Sir Paul McCartney and we were just in shock. He started singing along with the whole carriage and taking pictures. It was a once-in-a-lifetime experience.One of the best days of my life."Paul kicked off his impromptu performance with a rendition of 'A Hard Day's Night' before launching into a mash-up of the Fab Four's most famous tunes to cheers from thestunned passengers.Super-fan Robert Retz posted on Facebook: "As it turned out, he had security with him. He wanted to take a ride on a street car."Paul was also accompanied by his wife Nancy Shevell, 51, and the pair are staying in New Orleans to enjoy the annual Mardi Gras carnival and he was also at the Super Bowl NFLfinal last Sunday (February 3).