School of Medicine and Dentistry, University of Aberdeen, Aberdeen AB25 2ZD, UK. St George's University of London, London, UK. University of Southampton, Southampton, UK. St George's Healthcare NHS Trust, London, UK. Brighton and Sussex University Hospitals, Sussex, UK. The Queen Elizabeth Hospital, Adelaide, South Australia. University of Birmingham, Birmingham, UK. University of Edinburgh, Edinburgh, UK. School of Medicine and Dentistry, University of Aberdeen, Aberdeen AB25 2ZD, UK m.p.frenneaux@abdn.ac.uk.