1. Division of Surgery and Interventional Science, University College London, London, United Kingdom.
2. Department of Urology, University College London Hospital, London, United Kingdom.
3. School of Medicine, University of Glasgow, Glasgow, Scotland, United Kingdom.
4. Department of Anaesthesia and Perioperative Medicine, University College London Hospital, London, United Kingdom.
5. Department of Anaesthesia and Intensive Care, Papworth Hospital, Papworth, United Kingdom.