A sixth wedding anniversary would normally be a cause of joy and laughter. But when Justin and Hailey Bieber emerged from the Los Angeles restaurant where they had been celebrating theirs on Monday night, they looked like they were leaving a funeral. As his model wife, dressed down in jeans and a baggy jumper, walked several paces ahead of him, staring fixedly at the floor, the 30-year-old pop superstar followed behind, looking tense, his eyes and face hidden behind dark glasses and a baseball cap.

How different from a year ago when they released loving photos of one another amid mutual expressions of devotion online. One reason for their drained appearance could be the sleepless nights experienced by so many new parents – the birth of the couple’s first child, Jack Blues Bieber, was announced in August – but many suspect that they may have been under strain since Bieber’s friend and mentor, the music mogul Sean ‘Diddy’ Combs, was engulfed by a sex and abuse scandal. Last month, Diddy was sensationally charged with racketeering, ‘sex trafficking by force, fraud or coercion’ and ‘transportation to engage in prostitution’.

Since then, scores of accusers – male as well as female and including a boy as young as nine – have come forward to say, Combs, 54, sexually abused them, often in exchange for a promise to advance their music careers. When Canadian Bieber exploded into the pop world aged 15, he was taken in hand by Combs and by R&B star Usher, who owed.