1. Patrick Clements Clinic, Central Middlesex Hospital, Acton Lane, London NW10 7NS, UK
2. Mortimer Market Centre, Mortimer Market, off Capper Street, London WC1E 6AU, UK
3. Department of Clinical Audit & Effectiveness, Community Health South London NHS Trust, Elizabeth Blackwell House, Wardalls Grove, Avonley Road, London SE14 5ER, UK