In addition to Holter monitoring, 12-lead ECGs will be taken at baselines, 30 minutes into the experimental phase, at the end of the experimental phase and end of the clamp on both occasions. If there are any persisting QT changes at the end of the clamp, the participant will be invited to attend for a repeat ECG the next day to ensure that any ECG changes have resolved. There is a single case report of persisting QT interval prolongation for up to 48 hours after a period of hypoglycaemia in a 75 year old lady with end-stage renal disease in the context of acute myocardial ischaemia. Since we are recruiting from a younger population with no significant co-morbidities, we would not anticipate any lasting ECG changes.