Funding for this research was provided by:
UK Department of Health & Social Care
Received: 31 January 2020
Accepted: 30 April 2020
First Online: 25 May 2020
Ethics approval and consent to participate
: Ethical approval was obtained separately for each NMS. The original survey in 1995 was approved by the Trent Multi-Centre Research Ethics Committee (06/MREC/16). The most recent survey in 2018 was approved by the London Bloomsbury NRES Committee (18/LO/0271). The return of completed questionnaires was taken as indicating consent to participate.
: Not applicable.
: The authors have no competing interests to declare.