title: Authors' reply to Mannion.
authors.affiliation: Department of Primary Care and Public Health, Imperial College London, London, UK.
authors.forename: Jack
authors.initials: J
authors.lastname: Carruthers
authors.affiliation: Department of Medicine, Imperial College London, London, UK.
authors.forename: Alison
authors.initials: A
authors.lastname: Holmes
authors.affiliation: Department of Primary Care and Public Health, Imperial College London, London, UK.
authors.forename: Azeem
authors.initials: A
authors.lastname: Majeed