The next step is to evaluate use of the closed loop system day and night over a period of 7 days (phase 1) and 21 days (phase 2) in adolescents with type 1 diabetes. In the present study we are planning to study 24 (12 phase 1 ans 12 phase 2) young people aged 10-18 years on insulin pump therapy. This study will involve two 7 (phase 1) and 21 (phase 2) day home study periods, during which glucose levels will be controlled either by an automated closed-loop system or by subjects usual insulin pump therapy combined with continuous glucose monitoring alone in random order. Prior to the closed-loop study period, there will be a training period in the clinical research facility, which will allow participants to familiarise themselves with the closed-loop system before going home.