A rock star entering rehab is usually par for the course, yet there was widespread disbelief when Tom Chaplin, the angelic-voiced frontman of Keane, went public with his drug and alcohol problems back in 2006.

The revelation was completely at odds with his squeaky-clean public image and made him an easy target, ripe for mockery – Kasabian famously quipped the singer was “addicted to port” – but Chaplin’s issues were no laughing matter.

In his descent into self-destruction, Chaplin even ...