LOS ANGELES (Reuters) - Paul McCartney is set to wed for the third time after proposing to his New York businesswoman girlfriend of four years, Nancy Shevell. The London-based spokesman for the former Beatle confirmed on Friday that McCartney and Shevell were engaged, but declined to give further details. Its true said spokesman Stuart Bell, after People magazine broke news of the engagement. Shevell, 51, who is divorced, and the notoriously private McCartney, 68, are reported to have begun dating about four years ago, following the Fab Four singers bitter split with second wife, Heather Mills. People magazine said McCartney had given Shevell a ring, although she did not appear to be wearing it when the couple posed on the red carpet at Mondays museum event.