Richard Branson's airline Virgin Atlantic is under mounting pressure to explain how an insider was apparently able to pass the confidential flight details of as many as 70 celebrities to a major paparazzi agency. Emails sent to the Big Pictures agency in 2010 and 2011 contained the flight details of dozens of celebrities, including Madonna, Princess Beatrice and Sienna Miller. Some of the figures alleged to be affected are friends of Sir Richard and his family and the allegations could prove hugely embarrassing for the tycoon, who is known for his close ties to the world of show business. A senior employee is understood to have resigned on Thursday after initial allegations that she passed on the flight details of eight celebrities including the singer Cheryl Cole and her former husband,...