Footnotes

• Contributors Both authors have contributed to the preparation, refinement and review of the article and are in agreement with its content.

• Funding TWJ is supported by the NIHR Biomedical Research Centre at the University Hospitals Bristol NHS Foundation Trust and the University of Bristol.

• Disclaimer The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health.

• Competing interests None declared.

• Patient consent Not required.

• Provenance and peer review Commissioned; externally peer reviewed.