Funding for this research was provided by:
National Institute for Health Research
Article History
Received: 21 June 2018
Accepted: 4 October 2018
First Online: 30 October 2018
Ethical approval and consent to participate
: Not applicable.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.