One Direction's long-standing tour manager is believed to have quit and flown home from the US following a row with singer Zayn Malik. Paul Higgins has worked with the band since 2010 and was known as 'Daddy' due to his close relationship with the lads, especially fellow Irish man Niall Horan. However, Mirror Online has claimed that Higgins has now left the band following a disagreement with Malik, who has been at the centre of controversy in recent weeks after presenter Matt Lauer suggested that he was involved in "substance abuse". “There have been issues behind the scenes for a while, and they’ve finally come to a head leading to Paul’s relationship with the band coming to an end,” said a source. “In many ways, he has completely run the show while they’ve been on tour – they even call him Daddy. He became a friend as well as a key part of their management set-up. He’s always been at the heart of the One Direction team, and it’s hard to think of them going on tour without him there.” It's believed that the argument may have flared up while the boys were in London recording Band Aid 30 with Bob Geldof and could be the reason that Malik did not initially fly to the US to continue promo for the band's new album Four.