People with type 1 diabetes need regular insulin injections or continuous delivery of insulin using an insulin pump. Keeping blood sugars in the normal range is known to reduce the risk of long term complications involving the eyes, kidneys and heart. However, achieving treatment goals can be very difficult as the tighter we try to control blood glucose levels, the greater the risk of the person developing episodes of low glucose levels (hypoglycaemia). One solution is using a system where the amount of insulin injected closely matches the blood sugar levels on a continuous basis. This can be achieved by what is known as a "closed loop system" where a small glucose sensor placed under the skin communicates with a computer containing an algorithm that drives a subcutaneous insulin pump. This system is being developed in Cambridge and is undergoing trials in children and adults with type 1 diabetes. Results thus far show that the system is very effective at preventing hypoglycaemia and maintaining blood glucose levels in target range.