Footnotes

• Twitter @mgtmccartney, @carlheneghan

• Contributors MM wrote the article after discussion with other authors and who all edited and contributed thereafter. This has arisen over discussions with CH over many years.

• 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.

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