1. Centre for Research in Primary and Community Care, University of Hertfordshire, College Lane, Hatfield, Herts, AL10 9AB, UK
2. Centre for Research in Primary and Community Care, University of Hertfordshire, College Lane, Hatfield, Herts, AL10 9AB, UK, School of Nursing and Midwifery, University of Hertfordshire, College Lane, Hatfield, Herts, AL10 9AB, UK,
3. Institute of Neurology, University College, London, UK
4. Kings College Hospital and Kent and Canterbury Hospital, UK