Footnotes

• Twitter @damian_roland

• Contributors The original idea was conceived by DR and JW. JW and PAS wrote initial drafts and completed data collection. AC provided data analysis support.

• 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 JW, AS and DR are members of the National PEWS steering committee.

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