URINE SAMPLING 40ml urine samples will be taken after voiding every two hours, from 0h to 8h on day 1, and again at 24h (09.00 on day 3) and 72h (09.00 on day 5). Participants will be asked to void urine on waking on days 3 and 5. At the end of each study, the venous cannulae will be removed and haemostasis confirmed. Subjects will be provided with toast and a warm beverage and observed for 30 minutes before leaving the unit.