In the UK, the PARROT trial is funded by the NIHR HTA programme (ref 16/17/01). In Australia, the PARROT trial is funded by the National Health and Medical Research Council (NHMRC, ref 1157228, APP1149332). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, NHMRC or the Department of Health and social care.