1. Warwick Research in Nursing, Department of Health Sciences, Warwick Medical School, The University of Warwick, Gibbet Hill, Coventry, UK
2. On behalf of the CHESS team; Warwick Clinical Trials Unit, Warwick Medical School, The University of Warwick, Gibbet Hill, Coventry, UK
3. Warwick Clinical Trials Unit, Warwick Medical School, The University of Warwick, Gibbet Hill, Coventry, UK
4. Headache Group, UCL Institute of Neurology, Queen Square, London, UK