As a junior doctor in the UK, Kevin Murphy said he was “hideously addicted” to nicotine and would creep off the hospital campus to have a smoke, wearing disposable gloves and, on his way back, chewing as many mints as possible.

Before doing medicine, he’d worked as a radiographer and had seen “loads of lung cancer”. Then he was at his mother’s side when her 40-a-day habit for 40 years ended in lung cancer too.