1. London School of Hygiene and Tropical Medicine, 219, 15-17 Tavistock Place, London WC1H 9SH, UK
2. Cardiff University, Centre for the Development and Evaluation of Complex Interventions for Public Health Improvement (DECIPHer), School of Social Sciences, Cardiff University, Cardiff, CF10 3WT, UK
3. Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK.
4. UCL Institute of Education, 18 Woburn Square, London WC1H 0NR, UK.
5. School of Social and Community Medicine, University of Bristol, Office 4.06, Canynge Hall, 39 Whatley Road, Bristol BS8 2PS, UK.
6. London School of Hygiene and Tropical Medicine, 218, 15-17 Tavistock Place, London WC1H 9SH, UK.