[1] Univ London Imperial Coll Sci Technol & Med, Sch Business, London SW7 2AZ, England
[2] Univ London Imperial Coll Sci Technol & Med, Dept Primary Care & Publ Hlth, London W6 8RP, England
[3] Univ London Imperial Coll Sci Technol & Med, NIHR CLAHRC Northwest London, London SW10 9NH, England