Visit one (baseline, research facility or participant's home) Participants will attend non-fasting. Following written informed consent, a blood sample (approximately 30mls in total) will be taken for baseline measurements (to include C-peptide, glucose, HbA1c, creatinine, liver function) and saved serum and plasma. A urine sample will be collected and stored and a pregnancy test offered to pre-menopausal women. Baseline data will include: height, weight, age, duration of diabetes, age of diagnosis and ethnicity, and confirmation of treatment regimen. A standard hypoglycaemia questionnaire (the Modified Clarke/Edinburgh Hypoglycaemia questionnaire, incorporating the Gold question) will be completed by the participant. The participant's ability to self-monitor blood glucose will be confirmed (with further education provided if necessary). Participants will be instructed on the use of the CGM system, and requirements for self-monitoring of blood glucose. Whilst wearing the continuous glucose monitors participants will be requested to test their own blood glucose levels 4 times spread over the course of each day (for subsequent calibration purposes) and record this on a data collection sheet provided. They will also be asked to record details of meals, exercise or symptoms over the duration of monitoring. The automatic device will be set up for 4-6 days continuous glucose monitoring.