Footnotes

• Contributors Both authors conceived the idea equally with a mention to the commanding officer of 1 Scots Lt Col Andy Watson, who tasked the design. JBTH had the device built and PA oversaw this. The letter was written mostly by JBTH with PA's oversight and input. Both approved the final version for publication.

• 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; internally peer reviewed.