Footnotes

• Contributors All of the authors contributed to the development of the study. AB and AF developed the data capture tools and provided the analysis. CN collected the data and put in place the agreements to share data between independent organisations. SG, JE, PW, AE and MCM provided interpretation of the data. All authors reviewed the drafts and approved the final draft. JN wrote the manuscript.

• Funding This study was funded by James Knott Trust.

• Competing interests None declared.

• Patient consent for publication Not required.

• Provenance and peer review Not commissioned; internally peer reviewed.