Inclusion Criteria:  Age between 10 and 18 years of age Type 1 diabetes for at least 6 months Insulin pump user for at least 3 months Total daily dose of insulin >8 units/day Treated with rapid acting insulin analogue Subject/carer is willing to perform at least 2 finger-prick blood glucose measurements per day Screening HbA1c ≤ 11 % (97 mmol/mol) based on analysis from local laboratory Willing to wear glucose sensor Willing to wear closed loop system 24/7 The subject is willing to follow study specific instructions The subject/carer is willing to upload pump and CGM data at regular intervals  Exclusion Criteria:  Physical or psychological disease likely to interfere with normal conduct of the study Untreated coeliac disease or thyroid disease Current treatment with drugs known to interfere with glucose metabolism Participation in another interventional clinical investigation Treated with ultra-rapid acting insulin analogue Known or suspected allergy to insulin Carer's lack of reliable telephone facility for contact Subject's severe visual impairment Subject's severe hearing impairment Medically documented allergy towards the adhesive (glue) of plasters or subject is unable to tolerate tape adhesive in the area of sensor placement Serious skin diseases located at places of the body corresponding with sensor insertion sites Sickle cell disease, haemoglobinopathy; or has received red blood cell transfusion or erythropoietin within 3 months prior to time of screening