Bibliographical noteFunding Information:
Funding This study was funded by the National Institute for Health Research (NIHR) Policy Research Programme, funder reference: PR-PRU-1217-21301; UCL award code: 177763. The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.
© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.