Division of Surgery, University of Western Australia, Fiona Stanley Hospital, Perth, WA, Australia; Institute of Clinical Trials and Methodology, University College London, London, UK; Division of Surgery, University College London, London, UK. Electronic address: toby.richards@uwa.edu.au. Royal Marsden NHS Foundation Trust, London, UK. Department of Anaesthesia, Royal National Orthopaedic Hospital, London, UK. Division of Surgery, University College London, London, UK. Institute of Clinical Trials and Methodology, University College London, London, UK; Division of Surgery, University College London, London, UK. Department of Renal Medicine, King's College Hospital, London, UK. NIHR Leicester Biomedical Research Centre, Department of Cardiovascular Sciences, University of Leicester, Leicester, UK. Clinical Trials Unit, London School of Hygiene & Tropical Medicine, London, UK. School of Public Health, University College Cork, Cork, Ireland. University Department of Vascular Surgery, Birmingham University, Solihull Hospital, Solihull, UK. Department of Cardiology (CVK), Berlin Institute of Health Center for Regenerative Therapies, and German Centre for Cardiovascular Research partner site Berlin, Charité Universitätsmedizin Berlin, Berlin, Germany. Department of Anaesthesia and Intensive Care, Royal Papworth Hospital, Cambridge, UK.