Footnotes

• Contributors SH: involved in the planning, conduct and reporting of the work described in this article. RH: involved in the planning and reporting of the work described in this article. KT: involved in the critical revision of the work and final approval of the version to be published. JH: involved in the critical revision of the work and final approval of the version to be published.

• 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 Not commissioned; externally peer reviewed.