Footnotes

• Contributors RA prepared the original draft and provided significant input to later versions of the manuscript. AvR provided significant contributions to earlier versions of the manuscript. BB provided the idea for the manuscript, contributed to its early design and reviewed the final version of the manuscript.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Patient consent for publication Not required.

• Provenance and peer review Commissioned. Externally peer-reviewed by Simon Lewis, Sydney, Australia, and Ed Newman, Glasgow, UK.